Bump version.

.github/workflows/beta-release.yml

@@ -0,0 +1,187 @@
+name: Manual Beta Release
+
+on:
+  workflow_dispatch:
+    inputs:
+      release_title:
+        description: Optional GitHub release title override
+        required: false
+        type: string
+
+permissions:
+  contents: write
+  packages: read
+
+jobs:
+  release-beta:
+    name: Build and publish beta release
+    runs-on: windows-latest
+    env:
+      PROJECT_PATH: Wino.Mail.WinUI/Wino.Mail.WinUI.csproj
+      MANIFEST_PATH: Wino.Mail.WinUI/Package.appxmanifest
+      CHANGELOG_PATH: CHANGELOG.md
+      NUGET_CONFIG_PATH: ${{ github.workspace }}\nuget.config
+      PACKAGE_OUTPUT_DIR: ${{ github.workspace }}\artifacts\package
+      RELEASE_OUTPUT_DIR: ${{ github.workspace }}\artifacts\release
+      CERTIFICATE_PFX_PATH: ${{ github.workspace }}\artifacts\signing\beta-signing-cert.pfx
+      CERTIFICATE_CER_PATH: ${{ github.workspace }}\artifacts\release\Wino-Mail-Beta.cer
+    steps:
+      - name: Checkout selected branch
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.ref }}
+          fetch-depth: 0
+
+      - name: Fetch tags from origin
+        shell: pwsh
+        run: git fetch origin --force --tags
+
+      - name: Validate release secrets
+        shell: pwsh
+        env:
+          BETA_SIGNING_CERT_PFX_BASE64: ${{ secrets.BETA_SIGNING_CERT_PFX_BASE64 }}
+        run: |
+          if ([string]::IsNullOrWhiteSpace($env:BETA_SIGNING_CERT_PFX_BASE64)) {
+            throw "Missing required secret: BETA_SIGNING_CERT_PFX_BASE64"
+          }
+
+      - name: Setup .NET SDK
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 10.0.x
+        env:
+          NUGET_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Compute beta version and release metadata
+        id: metadata
+        shell: pwsh
+        env:
+          RELEASE_TITLE_INPUT: ${{ github.event.inputs.release_title }}
+        run: |
+          $manifestPath = Join-Path $env:GITHUB_WORKSPACE $env:MANIFEST_PATH
+          if (-not (Test-Path $manifestPath)) {
+            throw "Package manifest not found: $manifestPath"
+          }
+
+          $changelogPath = Join-Path $env:GITHUB_WORKSPACE $env:CHANGELOG_PATH
+          if (-not (Test-Path $changelogPath)) {
+            throw "Release notes file not found: $changelogPath"
+          }
+
+          [xml]$manifest = Get-Content -LiteralPath $manifestPath
+          $identityNode = $manifest.Package.Identity
+          if (-not $identityNode) {
+            throw "Could not locate the Package/Identity node in $manifestPath"
+          }
+
+          $currentVersionText = [string]$identityNode.Version
+          if ($currentVersionText -notmatch '^(?<major>\d+)\.(?<minor>\d+)\.(?<patch>\d+)\.(?<revision>\d+)$') {
+            throw "Manifest version '$currentVersionText' is not a four-part numeric version."
+          }
+
+          $packageVersion = $currentVersionText
+          $releaseTag = "v$packageVersion"
+          $releaseTitleInput = $env:RELEASE_TITLE_INPUT
+          $releaseTitle = if ([string]::IsNullOrWhiteSpace($releaseTitleInput)) { $releaseTag } else { $releaseTitleInput.Trim() }
+
+          $headSha = (git rev-parse HEAD).Trim()
+          if ([string]::IsNullOrWhiteSpace($headSha)) {
+            throw "Failed to resolve the checked out commit SHA."
+          }
+
+          $notesInput = Get-Content -LiteralPath $changelogPath -Raw
+          if ([string]::IsNullOrWhiteSpace($notesInput)) {
+            throw "Release notes file is empty: $changelogPath"
+          }
+
+          $notesInput = $notesInput.Trim()
+          New-Item -ItemType Directory -Path $env:RELEASE_OUTPUT_DIR -Force | Out-Null
+          $releaseNotesPath = Join-Path $env:RELEASE_OUTPUT_DIR 'beta-release-notes.md'
+          $notesInput | Set-Content -LiteralPath $releaseNotesPath -Encoding utf8
+
+          "package_version=$packageVersion" >> $env:GITHUB_OUTPUT
+          "release_tag=$releaseTag" >> $env:GITHUB_OUTPUT
+          "release_title=$releaseTitle" >> $env:GITHUB_OUTPUT
+          "release_notes_path=$releaseNotesPath" >> $env:GITHUB_OUTPUT
+          "head_sha=$headSha" >> $env:GITHUB_OUTPUT
+
+      - name: Materialize signing certificate
+        shell: pwsh
+        env:
+          BETA_SIGNING_CERT_PFX_BASE64: ${{ secrets.BETA_SIGNING_CERT_PFX_BASE64 }}
+        run: |
+          $signingDir = Split-Path -Parent $env:CERTIFICATE_PFX_PATH
+          New-Item -ItemType Directory -Path $signingDir -Force | Out-Null
+          [IO.File]::WriteAllBytes($env:CERTIFICATE_PFX_PATH, [Convert]::FromBase64String($env:BETA_SIGNING_CERT_PFX_BASE64))
+
+          $certificate = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2($env:CERTIFICATE_PFX_PATH, $null, [System.Security.Cryptography.X509Certificates.X509KeyStorageFlags]::Exportable)
+
+          New-Item -ItemType Directory -Path (Split-Path -Parent $env:CERTIFICATE_CER_PATH) -Force | Out-Null
+          [IO.File]::WriteAllBytes($env:CERTIFICATE_CER_PATH, $certificate.Export([System.Security.Cryptography.X509Certificates.X509ContentType]::Cert))
+
+      - name: Restore WinUI project dependencies
+        shell: pwsh
+        run: |
+          if (-not (Test-Path $env:NUGET_CONFIG_PATH)) {
+            throw "NuGet config file not found: $env:NUGET_CONFIG_PATH"
+          }
+
+          dotnet restore $env:PROJECT_PATH `
+            --configfile $env:NUGET_CONFIG_PATH `
+            -p:Platform=x64 `
+            /p:RestoreConfigFile="$env:NUGET_CONFIG_PATH"
+
+      - name: Build MSIX bundle
+        shell: pwsh
+        run: |
+          New-Item -ItemType Directory -Path $env:PACKAGE_OUTPUT_DIR -Force | Out-Null
+
+          dotnet build $env:PROJECT_PATH `
+            --configuration Release `
+            --no-restore `
+            --configfile $env:NUGET_CONFIG_PATH `
+            /p:Platform=x64 `
+            /p:RestoreConfigFile="$env:NUGET_CONFIG_PATH" `
+            /p:GenerateAppxPackageOnBuild=true `
+            /p:UapAppxPackageBuildMode=SideloadOnly `
+            /p:AppxBundle=Always `
+            /p:AppxBundlePlatforms="x86|x64|arm64" `
+            /p:AppxPackageDir="$env:PACKAGE_OUTPUT_DIR\\" `
+            /p:AppxPackageVersion=${{ steps.metadata.outputs.package_version }} `
+            /p:PackageCertificateKeyFile="$env:CERTIFICATE_PFX_PATH" `
+            /p:PackageCertificatePassword= `
+            /p:PackageCertificateThumbprint= `
+            /p:AppxPackageSigningEnabled=true
+
+      - name: Collect packaged artifacts
+        id: package
+        shell: pwsh
+        run: |
+          $bundle = Get-ChildItem -Path $env:PACKAGE_OUTPUT_DIR -Recurse -Filter *.msixbundle | Select-Object -First 1
+          if (-not $bundle) {
+            throw "No .msixbundle file was generated under $env:PACKAGE_OUTPUT_DIR"
+          }
+
+          $releaseAssetPath = Join-Path $env:RELEASE_OUTPUT_DIR "Wino_${{ steps.metadata.outputs.package_version }}.zip"
+          if (Test-Path $releaseAssetPath) {
+            Remove-Item -LiteralPath $releaseAssetPath -Force
+          }
+
+          Compress-Archive -LiteralPath @($bundle.FullName, $env:CERTIFICATE_CER_PATH) -DestinationPath $releaseAssetPath -Force
+
+          "bundle_path=$($bundle.FullName)" >> $env:GITHUB_OUTPUT
+          "bundle_name=$($bundle.Name)" >> $env:GITHUB_OUTPUT
+          "release_asset_path=$releaseAssetPath" >> $env:GITHUB_OUTPUT
+
+      - name: Create GitHub prerelease
+        shell: pwsh
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh release create "${{ steps.metadata.outputs.release_tag }}" `
+            "${{ steps.package.outputs.release_asset_path }}" `
+            --repo "${{ github.repository }}" `
+            --target "${{ steps.metadata.outputs.head_sha }}" `
+            --title "${{ steps.metadata.outputs.release_title }}" `
+            --notes-file "${{ steps.metadata.outputs.release_notes_path }}" `
+            --prerelease

.github/workflows/pr-winui-build.yml

@@ -1,125 +0,0 @@
-name: PR WinUI Build
-
-on:
-  pull_request:
-    types:
-      - opened
-      - synchronize
-      - reopened
-      - ready_for_review
-
-permissions:
-  contents: read
-  packages: read
-
-jobs:
-  build-winui:
-    name: Build project (${{ matrix.platform }})
-    if: github.event.pull_request.draft == false
-    runs-on: windows-latest
-    continue-on-error: ${{ contains(fromJSON('["OWNER","MEMBER","COLLABORATOR"]'), github.event.pull_request.author_association) }}
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - platform: x86
-            rid: win-x86
-          - platform: x64
-            rid: win-x64
-          - platform: ARM64
-            rid: win-arm64
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-
-      - name: Setup .NET SDK
-        uses: actions/setup-dotnet@v4
-        with:
-          dotnet-version: 10.0.x
-          source-url: https://nuget.pkg.github.com/bkaankose/index.json
-        env:
-          NUGET_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
-      - name: Restore WinUI project dependencies
-        run: dotnet restore Wino.Mail.WinUI/Wino.Mail.WinUI.csproj --configfile nuget.config -p:Platform=${{ matrix.platform }} -p:RuntimeIdentifier=${{ matrix.rid }}
-
-      - name: Build WinUI project
-        run: dotnet build Wino.Mail.WinUI/Wino.Mail.WinUI.csproj --configuration Release --no-restore -p:Platform=${{ matrix.platform }} -p:RuntimeIdentifier=${{ matrix.rid }} -p:GenerateAppxPackageOnBuild=false -p:AppxPackageSigningEnabled=false
-
-  core-tests:
-    name: Run Core tests
-    if: github.event.pull_request.draft == false
-    runs-on: windows-latest
-    continue-on-error: ${{ contains(fromJSON('["OWNER","MEMBER","COLLABORATOR"]'), github.event.pull_request.author_association) }}
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-
-      - name: Setup .NET SDK
-        uses: actions/setup-dotnet@v4
-        with:
-          dotnet-version: 10.0.x
-          source-url: https://nuget.pkg.github.com/bkaankose/index.json
-        env:
-          NUGET_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
-      - name: Restore Core test projects
-        shell: pwsh
-        run: |
-          $coreTests = Get-ChildItem -Path . -Recurse -Filter "*Core*.Tests.csproj" | ForEach-Object { $_.FullName }
-          if (-not $coreTests) {
-            throw "No Core test projects were found."
-          }
-
-          foreach ($project in $coreTests) {
-            dotnet restore $project --configfile nuget.config
-          }
-
-      - name: Run Core test projects
-        shell: pwsh
-        run: |
-          New-Item -ItemType Directory -Path TestResults -Force | Out-Null
-          $coreTests = Get-ChildItem -Path . -Recurse -Filter "*Core*.Tests.csproj"
-          if (-not $coreTests) {
-            throw "No Core test projects were found."
-          }
-
-          foreach ($project in $coreTests) {
-            $name = $project.BaseName
-            dotnet test $project.FullName --configuration Release --no-restore --verbosity normal --logger "trx;LogFileName=$name.trx" --results-directory TestResults
-          }
-
-      - name: Upload Core test result artifacts
-        if: always()
-        uses: actions/upload-artifact@v4
-        with:
-          name: core-test-results
-          path: TestResults/*.trx
-          if-no-files-found: warn
-
-      - name: Publish Core test report
-        if: always()
-        uses: EnricoMi/publish-unit-test-result-action/windows@v2
-        with:
-          trx_files: TestResults/*.trx
-          check_name: Core test results
-
-  enforce-for-non-maintainers:
-    name: Enforce required checks (non-maintainers)
-    if: github.event.pull_request.draft == false && !contains(fromJSON('["OWNER","MEMBER","COLLABORATOR"]'), github.event.pull_request.author_association)
-    runs-on: ubuntu-latest
-    needs:
-      - build-winui
-      - core-tests
-
-    steps:
-      - name: Fail when build or tests fail for non-maintainers
-        if: needs.build-winui.result != 'success' || needs.core-tests.result != 'success'
-        run: |
-          echo "WinUI build and Core tests must pass for non-maintainer pull requests."
-          exit 1
-
-      - name: Confirm build and test success for non-maintainers
-        run: echo "WinUI build and Core tests passed."

AGENTS.md

@@ -150,6 +150,8 @@ private string searchQuery = string.Empty;
 - For dependency properties in WinUI code, always prefer `[GeneratedDependencyProperty]` from CommunityToolkit over manual `DependencyProperty.Register(...)` declarations.
 - When a `[RelayCommand]` needs enable/disable logic, prefer the command's `CanExecute` over binding `Button.IsEnabled` in XAML; use `[NotifyCanExecuteChangedFor]` on dependent properties and call `NotifyCanExecuteChanged()` explicitly when non-generated state affects the command.
 - In ViewModels, update all UI-bound properties/collections via `ExecuteUIThread(...)` (especially after awaited calls and any use of `ConfigureAwait(false)`).
+- `ConfigureAwait(false)` continues execution on a background thread. Any UI-bound property change, `INotifyPropertyChanged` notification, collection mutation, or similar UI-facing state update after that point must be marshaled back with `ExecuteUIThread(...)` or the appropriate dispatcher call, otherwise the app can crash.
+- Messenger messages are raised from a background thread by default, while UI control event handlers such as `Button.Click` start on the UI thread. Be deliberate when combining dispatcher usage with `ConfigureAwait(false)` so post-await UI updates always return to the UI thread.
 - ViewModels should only handle UI interaction/state and delegate business logic to services; account-management work belongs in `WinoAccountProfileService`, and preferences import/export/apply logic belongs in `PreferencesService`.
 - In `EventDetailsPageViewModel.LoadAttendeesAsync`, never mutate `CurrentEvent.Attendees` outside `ExecuteUIThread(...)`.
 - Never create pure C# controls or controls that heavily manipulate UI structure from `.cs` files. Define controls in XAML and keep UI composition in XAML.

Wino.Calendar.ViewModels/CalendarAppShellViewModel.cs

@@ -169,6 +169,7 @@ public partial class CalendarAppShellViewModel : CalendarBaseViewModel,
 
         var activationContext = parameters as ShellModeActivationContext;
         var shouldRunStartupFlows = activationContext?.IsInitialActivation ?? true;
+        var navigationArgs = activationContext?.Parameter as CalendarPageNavigationArgs;
 
         PreferencesService.PreferenceChanged -= PreferencesServiceChanged;
         PreferencesService.PreferenceChanged += PreferencesServiceChanged;
@@ -178,19 +179,14 @@ public partial class CalendarAppShellViewModel : CalendarBaseViewModel,
         await InitializeAccountCalendarsAsync();
         ValidateConfiguredNewEventCalendar();
 
-        if (activationContext?.Parameter is CalendarItemTarget calendarItemTarget)
+        if (navigationArgs != null)
         {
-            NavigationService.Navigate(WinoPage.EventDetailsPage, calendarItemTarget);
+            NavigationService.Navigate(WinoPage.CalendarPage, navigationArgs);
-            return;
         }
-
+        else if (shouldRunStartupFlows || _calendarPageViewModel.CurrentVisibleRange == null)
-        if (activationContext?.Parameter is CalendarPageNavigationArgs calendarPageNavigationArgs)
         {
-            NavigationService.Navigate(WinoPage.CalendarPage, calendarPageNavigationArgs);
+            TodayClicked();
-            return;
         }
-
-        TodayClicked();
     }
 
     public override void OnNavigatedFrom(NavigationMode mode, object parameters)

Wino.Calendar.ViewModels/CalendarPageViewModel.cs

@@ -86,6 +86,7 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
         get
         {
             if (SelectedQuickEventAccountCalendar == null ||
+                SelectedQuickEventAccountCalendar.IsReadOnly ||
                 SelectedQuickEventDate == null ||
                 string.IsNullOrWhiteSpace(EventName) ||
                 string.IsNullOrWhiteSpace(SelectedStartTimeString) ||
@@ -204,6 +205,12 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
         if (DisplayDetailsCalendarItemViewModel?.CalendarItem == null)
             return;
 
+        if (DisplayDetailsCalendarItemViewModel.AssignedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
+
         if (DisplayDetailsCalendarItemViewModel.CalendarItem.IsRecurringParent)
         {
             var confirmed = await _dialogService.ShowConfirmationDialogAsync(
@@ -460,6 +467,12 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
     [RelayCommand(AllowConcurrentExecutions = false, CanExecute = nameof(CanSaveQuickEvent))]
     private async Task SaveQuickEventAsync()
     {
+        if (SelectedQuickEventAccountCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
+
         var startDate = IsAllDay ? SelectedQuickEventDate.Value.Date : QuickEventStartTime;
         var endDate = IsAllDay ? SelectedQuickEventDate.Value.Date.AddDays(1) : QuickEventEndTime;
         var composeResult = new CalendarEventComposeResult
@@ -553,6 +566,12 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
             return;
         }
 
+        if (calendarItem.AssignedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
+
         var normalizedTargetStart = calendarItem.IsAllDayEvent
             ? targetStart.Date
             : targetStart;
@@ -615,7 +634,7 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
         }
     }
 
-    public async Task ApplyDisplayRequestAsync(CalendarDisplayRequest request, bool forceReload = false)
+    public async Task ApplyDisplayRequestAsync(CalendarDisplayRequest request, bool forceReload = false, CalendarItemTarget pendingTarget = null)
     {
         var lifetimeVersion = CurrentPageLifetimeVersion;
         var hasLoadingLock = await WaitForCalendarLoadingLockAsync(lifetimeVersion).ConfigureAwait(false);
@@ -699,6 +718,11 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
             await _notificationBuilder.ClearCalendarTaskbarBadgeAsync().ConfigureAwait(false);
             _isCalendarBadgeClearedForPageLifetime = true;
         }
+
+        if (loadSucceeded && pendingTarget != null && IsPageActive(lifetimeVersion))
+        {
+            await NavigateToPendingCalendarTargetAsync(pendingTarget).ConfigureAwait(false);
+        }
     }
 
     public Task ReloadCurrentVisibleRangeAsync()
@@ -726,6 +750,31 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
         NavigateEvent(new CalendarItemViewModel(calendarItem), CalendarEventTargetType.Single);
     }
 
+    private async Task NavigateToPendingCalendarTargetAsync(CalendarItemTarget target)
+    {
+        CalendarItemViewModel calendarItemViewModel = null;
+
+        if (_loadedCalendarItems.TryGetValue(target.Item.Id, out var loadedCalendarItemViewModel))
+        {
+            calendarItemViewModel = loadedCalendarItemViewModel;
+        }
+        else
+        {
+            var targetItem = await _calendarService.GetCalendarItemTargetAsync(target).ConfigureAwait(false);
+            if (targetItem == null)
+                return;
+
+            targetItem.AssignedCalendar ??= AccountCalendarStateService.ActiveCalendars.FirstOrDefault(calendar => calendar.Id == targetItem.CalendarId);
+            calendarItemViewModel = new CalendarItemViewModel(targetItem);
+        }
+
+        await ExecuteUIThread(() =>
+        {
+            DisplayDetailsCalendarItemViewModel = calendarItemViewModel;
+            NavigateEvent(calendarItemViewModel, target.TargetType);
+        }).ConfigureAwait(false);
+    }
+
     private async Task<List<CalendarItemViewModel>> LoadCalendarItemsAsync(DateRange loadedDateWindow, long lifetimeVersion)
     {
         var loadedItems = new Dictionary<Guid, CalendarItemViewModel>();
@@ -800,7 +849,7 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
     }
 
     public async void Receive(LoadCalendarMessage message)
-        => await ApplyDisplayRequestAsync(message.DisplayRequest, message.ForceReload);
+        => await ApplyDisplayRequestAsync(message.DisplayRequest, message.ForceReload, message.PendingTarget);
 
     public void Receive(CalendarSettingsUpdatedMessage message)
     {
@@ -1195,6 +1244,12 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
         if (targetItem == null)
             return;
 
+        if (targetItem.AssignedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
+
         if (targetItem.IsRecurringParent)
         {
             var confirmed = await _dialogService.ShowConfirmationDialogAsync(
@@ -1221,6 +1276,12 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
         if (targetItem == null || targetItem.ShowAs == showAs)
             return;
 
+        if (targetItem.AssignedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
+
         var originalItem = await _calendarService.GetCalendarItemAsync(targetItem.Id).ConfigureAwait(false);
         var attendees = await _calendarService.GetAttendeesAsync(targetItem.Id).ConfigureAwait(false);
 
@@ -1245,6 +1306,12 @@ public partial class CalendarPageViewModel : CalendarBaseViewModel,
         if (targetItem == null)
             return;
 
+        if (targetItem.AssignedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
+
         var operation = responseStatus switch
         {
             CalendarItemStatus.Accepted => CalendarSynchronizerOperation.AcceptEvent,

Wino.Calendar.ViewModels/Data/AccountCalendarViewModel.cs

@@ -55,6 +55,12 @@ public partial class AccountCalendarViewModel : ObservableObject, IAccountCalend
         set => SetProperty(AccountCalendar.IsPrimary, value, AccountCalendar, (u, i) => u.IsPrimary = i);
     }
 
+    public bool IsReadOnly
+    {
+        get => AccountCalendar.IsReadOnly;
+        set => SetProperty(AccountCalendar.IsReadOnly, value, AccountCalendar, (u, i) => u.IsReadOnly = i);
+    }
+
     public bool IsSynchronizationEnabled
     {
         get => AccountCalendar.IsSynchronizationEnabled;

Wino.Calendar.ViewModels/EventDetailsPageViewModel.cs

@@ -440,6 +440,11 @@ public partial class EventDetailsPageViewModel : CalendarBaseViewModel
     private async Task SaveAsync()
     {
         if (CurrentEvent == null) return;
+        if (CurrentEvent.AssignedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
 
         try
         {
@@ -506,6 +511,11 @@ public partial class EventDetailsPageViewModel : CalendarBaseViewModel
     private async Task DeleteAsync()
     {
         if (CurrentEvent == null) return;
+        if (CurrentEvent.AssignedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
 
         // If the event is a master recurring event, ask for confirmation
         if (CurrentEvent.IsRecurringParent)
@@ -610,6 +620,11 @@ public partial class EventDetailsPageViewModel : CalendarBaseViewModel
     private async Task SendRsvpResponse(AttendeeStatus status)
     {
         if (CurrentEvent == null) return;
+        if (CurrentEvent.AssignedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
 
         try
         {

Wino.Core.Domain/Constants.cs

@@ -21,10 +21,10 @@ public static class Constants
     public const string ToastCalendarJoinOnlineAction = nameof(ToastCalendarJoinOnlineAction);
     public const string ToastCalendarSnoozeAction = nameof(ToastCalendarSnoozeAction);
     public const string ToastCalendarSnoozeDurationInputId = nameof(ToastCalendarSnoozeDurationInputId);
-    public const string ToastCalendarSnoozeDurationMinutesKey = nameof(ToastCalendarSnoozeDurationMinutesKey);
     public const string ToastModeKey = nameof(ToastModeKey);
     public const string ToastModeMail = nameof(ToastModeMail);
     public const string ToastModeCalendar = nameof(ToastModeCalendar);
+    public const string ToastDismissActionKey = nameof(ToastDismissActionKey);
     public const string ToastStoreUpdateActionKey = nameof(ToastStoreUpdateActionKey);
     public const string ToastStoreUpdateActionInstall = nameof(ToastStoreUpdateActionInstall);
     public const string ClientLogFile = "Client_.log";

Wino.Core.Domain/Entities/Calendar/AccountCalendar.cs

@@ -16,6 +16,7 @@ public class AccountCalendar : IAccountCalendar
     public string SynchronizationDeltaToken { get; set; }
     public string Name { get; set; }
     public bool IsPrimary { get; set; }
+    public bool IsReadOnly { get; set; }
     public bool IsSynchronizationEnabled { get; set; } = true;
     public bool IsExtended { get; set; } = true;
     public CalendarItemShowAs DefaultShowAs { get; set; } = CalendarItemShowAs.Busy;

Wino.Core.Domain/Entities/Mail/MailCategory.cs

@@ -0,0 +1,25 @@
+using System;
+using SQLite;
+using Wino.Core.Domain.Enums;
+
+namespace Wino.Core.Domain.Entities.Mail;
+
+public class MailCategory
+{
+    [PrimaryKey]
+    public Guid Id { get; set; }
+
+    public Guid MailAccountId { get; set; }
+
+    public string RemoteId { get; set; }
+
+    public string Name { get; set; }
+
+    public bool IsFavorite { get; set; }
+
+    public string BackgroundColorHex { get; set; }
+
+    public string TextColorHex { get; set; }
+
+    public MailCategorySource Source { get; set; } = MailCategorySource.Local;
+}

Wino.Core.Domain/Entities/Mail/MailCategoryAssignment.cs

@@ -0,0 +1,14 @@
+using System;
+using SQLite;
+
+namespace Wino.Core.Domain.Entities.Mail;
+
+public class MailCategoryAssignment
+{
+    [PrimaryKey]
+    public Guid Id { get; set; }
+
+    public Guid MailCategoryId { get; set; }
+
+    public Guid MailCopyUniqueId { get; set; }
+}

Wino.Core.Domain/Entities/Shared/MailAccount.cs

@@ -132,5 +132,10 @@ public class MailAccount
     /// </summary>
     public bool IsAliasSyncSupported => ProviderType == MailProviderType.Gmail || ProviderType == MailProviderType.Outlook;
 
+    /// <summary>
+    /// Gets whether the account can perform category definition sync type.
+    /// </summary>
+    public bool IsCategorySyncSupported => ProviderType == MailProviderType.Outlook;
+
     public override string ToString() => Name;
 }

Wino.Core.Domain/Enums/MailCategorySource.cs

@@ -0,0 +1,7 @@
+namespace Wino.Core.Domain.Enums;
+
+public enum MailCategorySource
+{
+    Local,
+    Outlook
+}

Wino.Core.Domain/Enums/MailOperation.cs

@@ -13,6 +13,7 @@ public enum MailSynchronizerOperation
     AlwaysMoveTo,
     MoveToFocused,
     Archive,
+    UpdateCategories,
 }
 
 public enum FolderSynchronizerOperation
@@ -35,6 +36,13 @@ public enum CalendarSynchronizerOperation
     TentativeEvent,
 }
 
+public enum CategorySynchronizerOperation
+{
+    CreateCategory,
+    UpdateCategory,
+    DeleteCategory,
+}
+
 // UI requests
 public enum MailOperation
 {

Wino.Core.Domain/Enums/MailSynchronizationType.cs

@@ -3,6 +3,7 @@
 public enum MailSynchronizationType
 {
     UpdateProfile, // Only update profile information
+    Categories, // Only update mail categories
     ExecuteRequests, // Run the queued requests, and then synchronize if needed.
     FoldersOnly, // Only synchronize folder metadata.
     InboxOnly, // Only Inbox, Sent, Draft and Deleted folders.

Wino.Core.Domain/Enums/WinoPage.cs

@@ -19,11 +19,13 @@ public enum WinoPage
     AboutPage,
     PersonalizationPage,
     MessageListPage,
+    MailNotificationSettingsPage,
     MailListPage,
     ReadComposePanePage,
     AppPreferencesPage,
     SettingOptionsPage,
     AliasManagementPage,
+    MailCategoryManagementPage,
     ImapCalDavSettingsPage,
     KeyboardShortcutsPage,
     CalendarPage,

Wino.Core.Domain/Interfaces/IAccountCalendar.cs

@@ -10,6 +10,7 @@ public interface IAccountCalendar
     string TextColorHex { get; set; }
     string BackgroundColorHex { get; set; }
     bool IsPrimary { get; set; }
+    bool IsReadOnly { get; set; }
     bool IsSynchronizationEnabled { get; set; }
     Guid AccountId { get; set; }
     string RemoteCalendarId { get; set; }

Wino.Core.Domain/Interfaces/IFolderMenuItem.cs

@@ -14,6 +14,22 @@ public interface IFolderMenuItem : IBaseFolderMenuItem
 
 public interface IMergedAccountFolderMenuItem : IBaseFolderMenuItem { }
 
+public interface IMailCategoryMenuItem : IBaseFolderMenuItem
+{
+    Entities.Mail.MailCategory MailCategory { get; }
+    string TextColorHex { get; }
+    string BackgroundColorHex { get; }
+    bool HasTextColor { get; }
+}
+
+public interface IMergedMailCategoryMenuItem : IBaseFolderMenuItem
+{
+    IReadOnlyList<Entities.Mail.MailCategory> Categories { get; }
+    string TextColorHex { get; }
+    string BackgroundColorHex { get; }
+    bool HasTextColor { get; }
+}
+
 public interface IBaseFolderMenuItem : IMenuItem
 {
     string FolderName { get; }

Wino.Core.Domain/Interfaces/IMailCategoryService.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Models.Accounts;
+
+namespace Wino.Core.Domain.Interfaces;
+
+public interface IMailCategoryService
+{
+    Task<List<MailCategory>> GetCategoriesAsync(Guid accountId);
+    Task<List<MailCategory>> GetFavoriteCategoriesAsync(Guid accountId);
+    Task<MailCategory> GetCategoryAsync(Guid categoryId);
+    Task<bool> CategoryNameExistsAsync(Guid accountId, string name, Guid? excludedCategoryId = null);
+    Task<MailCategory> CreateCategoryAsync(MailCategory category);
+    Task UpdateCategoryAsync(MailCategory category);
+    Task DeleteCategoryAsync(Guid categoryId);
+    Task DeleteCategoriesAsync(Guid accountId);
+    Task ToggleFavoriteAsync(Guid categoryId, bool isFavorite);
+    Task UpdateRemoteIdAsync(Guid categoryId, string remoteId);
+    Task ReplaceCategoriesAsync(Guid accountId, IEnumerable<MailCategory> categories);
+    Task ReplaceMailAssignmentsAsync(Guid accountId, Guid mailCopyUniqueId, IEnumerable<string> categoryNames);
+    Task AssignCategoryAsync(Guid categoryId, IEnumerable<Guid> mailCopyUniqueIds);
+    Task UnassignCategoryAsync(Guid categoryId, IEnumerable<Guid> mailCopyUniqueIds);
+    Task<List<MailCategory>> GetCategoriesForMailAsync(Guid accountId, IEnumerable<Guid> mailCopyUniqueIds);
+    Task<List<Guid>> GetAssignedCategoryIdsForAllAsync(IEnumerable<Guid> mailCopyUniqueIds);
+    Task<List<string>> GetCategoryNamesForMailAsync(Guid mailCopyUniqueId);
+    Task<List<MailCopy>> GetMailCopiesForCategoryAsync(Guid categoryId);
+    Task<List<UnreadCategoryCountResult>> GetUnreadCategoryCountResultsAsync(IEnumerable<Guid> accountIds);
+}

Wino.Core.Domain/Interfaces/IMailDialogService.cs

@@ -11,11 +11,13 @@ using Wino.Core.Domain.Models;
 using Wino.Core.Domain.Models.Accounts;
 using Wino.Core.Domain.Models.Calendar;
 using Wino.Core.Domain.Models.Folders;
+using Wino.Core.Domain.Models.MailItem;
 
 namespace Wino.Core.Domain.Interfaces;
 
 public interface IMailDialogService : IDialogServiceBase
 {
+    void ShowReadOnlyCalendarMessage();
     Task<bool> ShowHardDeleteConfirmationAsync();
     Task HandleSystemFolderConfigurationDialogAsync(Guid accountId, IFolderService folderService);
 
@@ -51,6 +53,13 @@ public interface IMailDialogService : IDialogServiceBase
     /// <returns>Created alias model if not canceled.</returns>
     Task<ICreateAccountAliasDialog> ShowCreateAccountAliasDialogAsync();
 
+    /// <summary>
+    /// Presents a dialog to the user for mail category creation/modification.
+    /// </summary>
+#pragma warning disable CS8625
+    Task<MailCategoryDialogResult> ShowEditMailCategoryDialogAsync(MailCategory category = null);
+#pragma warning restore CS8625
+
     /// <summary>
     /// Presents a dialog to the user to show email source.
     /// </summary>

Wino.Core.Domain/Interfaces/IPreferencesService.cs

@@ -192,6 +192,16 @@ public interface IPreferencesService : INotifyPropertyChanged
     /// </summary>
     Guid? StartupEntityId { get; set; }
 
+    /// <summary>
+    /// Setting: First action button displayed on mail toast notifications.
+    /// </summary>
+    MailOperation FirstMailNotificationAction { get; set; }
+
+    /// <summary>
+    /// Setting: Second action button displayed on mail toast notifications.
+    /// </summary>
+    MailOperation SecondMailNotificationAction { get; set; }
+
 
 
     /// <summary>

Wino.Core.Domain/Interfaces/IRequestBundle.cs

@@ -72,3 +72,9 @@ public interface ICalendarActionRequest : IRequestBase
     Guid? LocalCalendarItemId { get; }
     CalendarSynchronizerOperation Operation { get; }
 }
+
+public interface ICategoryActionRequest : IRequestBase
+{
+    Guid AccountId { get; }
+    CategorySynchronizerOperation Operation { get; }
+}

Wino.Core.Domain/Interfaces/ISynchronizationManager.cs

@@ -63,6 +63,12 @@ public interface ISynchronizationManager
     Task<MailSynchronizationResult> SynchronizeAliasesAsync(Guid accountId,
                                                             CancellationToken cancellationToken = default);
 
+    /// <summary>
+    /// Handles category synchronization for the given account.
+    /// </summary>
+    Task<MailSynchronizationResult> SynchronizeCategoriesAsync(Guid accountId,
+                                                               CancellationToken cancellationToken = default);
+
     /// <summary>
     /// Handles profile synchronization for the given account.
     /// </summary>

Wino.Core.Domain/Interfaces/IWinoRequestDelegator.cs

@@ -1,4 +1,6 @@
-using System.Threading.Tasks;
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
 using Wino.Core.Domain.Models.Calendar;
 using Wino.Core.Domain.Models.Folders;
 using Wino.Core.Domain.Models.MailItem;
@@ -36,4 +38,9 @@ public interface IWinoRequestDelegator
     /// </summary>
     /// <param name="calendarOperationPreparationRequest">Calendar preparation request.</param>
     Task ExecuteAsync(CalendarOperationPreparationRequest calendarOperationPreparationRequest);
+
+    /// <summary>
+    /// Queues pre-built requests for a single account and triggers synchronization.
+    /// </summary>
+    Task ExecuteAsync(Guid accountId, IEnumerable<IRequestBase> requests);
 }

Wino.Core.Domain/MenuItems/MailCategoryMenuItem.cs

@@ -0,0 +1,48 @@
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using CommunityToolkit.Mvvm.ComponentModel;
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Entities.Shared;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Interfaces;
+using Wino.Core.Domain.Models.Folders;
+
+namespace Wino.Core.Domain.MenuItems;
+
+public partial class MailCategoryMenuItem : MenuItemBase<MailCategory, IMenuItem>, IFolderMenuItem, IMailCategoryMenuItem
+{
+    private IReadOnlyList<IMailItemFolder> _handlingFolders;
+
+    [ObservableProperty]
+    private int unreadItemCount;
+
+    public MailCategoryMenuItem(MailCategory category, MailAccount parentAccount, IEnumerable<IMailItemFolder> handlingFolders, IMenuItem parentMenuItem)
+        : base(category, category.Id, parentMenuItem)
+    {
+        ParentAccount = parentAccount;
+        _handlingFolders = handlingFolders?.ToList() ?? [];
+    }
+
+    public string FolderName => Parameter.Name;
+    public bool IsSynchronizationEnabled => false;
+    public SpecialFolderType SpecialFolderType => SpecialFolderType.Other;
+    public IEnumerable<IMailItemFolder> HandlingFolders => _handlingFolders;
+    public new ObservableCollection<IMenuItem> SubMenuItems { get; } = [];
+    public bool IsMoveTarget => true;
+    public bool IsSticky => false;
+    public bool IsSystemFolder => false;
+    public bool ShowUnreadCount => true;
+    public string AssignedAccountName => ParentAccount?.Name;
+    public MailAccount ParentAccount { get; private set; }
+    public string TextColorHex => Parameter.TextColorHex;
+    public string BackgroundColorHex => Parameter.BackgroundColorHex;
+    public bool HasTextColor => !string.IsNullOrWhiteSpace(Parameter.TextColorHex);
+    public MailCategory MailCategory => Parameter;
+
+    public void UpdateFolder(IMailItemFolder folder)
+    {
+    }
+
+    public void UpdateParentAccounnt(MailAccount account) => ParentAccount = account;
+}

Wino.Core.Domain/MenuItems/MenuItemCollection.cs

@@ -22,11 +22,13 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
 
     public IEnumerable<IAccountMenuItem> GetAllAccountMenuItems()
     {
-        foreach (var item in this)
+        var rootItems = this.ToList();
+
+        foreach (var item in rootItems)
         {
             if (item is MergedAccountMenuItem mergedAccountMenuItem)
             {
-                foreach (var singleItem in mergedAccountMenuItem.SubMenuItems.OfType<IAccountMenuItem>())
+                foreach (var singleItem in mergedAccountMenuItem.SubMenuItems.OfType<IAccountMenuItem>().ToList())
                 {
                     yield return singleItem;
                 }
@@ -40,9 +42,11 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
 
     public IEnumerable<IBaseFolderMenuItem> GetAllFolderMenuItems(Guid folderId)
     {
-        foreach (var item in this)
+        var rootItems = this.ToList();
+
+        foreach (var item in rootItems)
         {
-            if (item is IBaseFolderMenuItem folderMenuItem)
+            if (item is IBaseFolderMenuItem folderMenuItem && item is not IMailCategoryMenuItem && item is not IMergedMailCategoryMenuItem)
             {
                 if (folderMenuItem.HandlingFolders.Any(a => a.Id == folderId))
                 {
@@ -50,7 +54,7 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
                 }
                 else if (folderMenuItem.SubMenuItems.Any())
                 {
-                    foreach (var subItem in folderMenuItem.SubMenuItems.OfType<IBaseFolderMenuItem>())
+                    foreach (var subItem in folderMenuItem.SubMenuItems.OfType<IBaseFolderMenuItem>().ToList())
                     {
                         if (subItem.HandlingFolders.Any(a => a.Id == folderId))
                         {
@@ -65,8 +69,10 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
 
     public bool TryGetAccountMenuItem(Guid accountId, out IAccountMenuItem value)
     {
-        value = this.OfType<AccountMenuItem>().FirstOrDefault(a => a.AccountId == accountId);
+        var rootItems = this.ToList();
-        value ??= this.OfType<MergedAccountMenuItem>().FirstOrDefault(a => a.SubMenuItems.OfType<AccountMenuItem>().Where(b => b.AccountId == accountId) != null);
+
+        value = rootItems.OfType<AccountMenuItem>().FirstOrDefault(a => a.AccountId == accountId);
+        value ??= rootItems.OfType<MergedAccountMenuItem>().FirstOrDefault(a => a.SubMenuItems.OfType<AccountMenuItem>().Any(b => b.AccountId == accountId));
 
         return value != null;
     }
@@ -74,7 +80,9 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
     // Pattern: Look for special folder menu item inside the loaded folders for Windows Mail style menu items.
     public bool TryGetWindowsStyleRootSpecialFolderMenuItem(Guid accountId, SpecialFolderType specialFolderType, out FolderMenuItem value)
     {
-        value = this.OfType<IBaseFolderMenuItem>()
+        var rootItems = this.ToList();
+
+        value = rootItems.OfType<IBaseFolderMenuItem>()
                 .FirstOrDefault(a => a.HandlingFolders.Any(b => b.MailAccountId == accountId && b.SpecialFolderType == specialFolderType)) as FolderMenuItem;
 
         return value != null;
@@ -84,7 +92,9 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
     // This will not look for the folders inside individual account menu items inside merged account menu item.
     public bool TryGetMergedAccountSpecialFolderMenuItem(Guid mergedInboxId, SpecialFolderType specialFolderType, out IBaseFolderMenuItem value)
     {
-        value = this.OfType<MergedAccountFolderMenuItem>()
+        var rootItems = this.ToList();
+
+        value = rootItems.OfType<MergedAccountFolderMenuItem>()
                 .Where(a => a.MergedInbox.Id == mergedInboxId)
                 .FirstOrDefault(a => a.SpecialFolderType == specialFolderType);
 
@@ -93,11 +103,14 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
 
     public bool TryGetFolderMenuItem(Guid folderId, out IBaseFolderMenuItem value)
     {
+        var rootItems = this.ToList();
+
         // Root folders
-        value = this.OfType<IBaseFolderMenuItem>()
+        value = rootItems.OfType<IBaseFolderMenuItem>()
+                .Where(a => a is not IMailCategoryMenuItem && a is not IMergedMailCategoryMenuItem)
                 .FirstOrDefault(a => a.HandlingFolders.Any(b => b.Id == folderId));
 
-        value ??= this.OfType<FolderMenuItem>()
+        value ??= rootItems.OfType<FolderMenuItem>()
             .SelectMany(a => a.SubMenuItems)
                 .OfType<IBaseFolderMenuItem>()
                 .FirstOrDefault(a => a.HandlingFolders.Any(b => b.Id == folderId));
@@ -105,10 +118,23 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
         return value != null;
     }
 
+    public bool TryGetCategoryMenuItem(Guid categoryId, out IBaseFolderMenuItem value)
+    {
+        var rootItems = this.ToList();
+
+        value = rootItems.OfType<IMailCategoryMenuItem>()
+            .FirstOrDefault(a => a.MailCategory.Id == categoryId);
+
+        value ??= rootItems.OfType<IMergedMailCategoryMenuItem>()
+            .FirstOrDefault(a => a.Categories.Any(b => b.Id == categoryId)) as IBaseFolderMenuItem;
+
+        return value != null;
+    }
+
     public void UpdateUnreadItemCountsToZero()
     {
         // Handle the root folders.
-        foreach (var item in this.OfType<IBaseFolderMenuItem>())
+        foreach (var item in this.OfType<IBaseFolderMenuItem>().ToList())
         {
             RecursivelyResetUnreadItemCount(item);
         }
@@ -120,7 +146,7 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
 
         if (baseFolderMenuItem.SubMenuItems == null) return;
 
-        foreach (var subMenuItem in baseFolderMenuItem.SubMenuItems.OfType<IBaseFolderMenuItem>())
+        foreach (var subMenuItem in baseFolderMenuItem.SubMenuItems.OfType<IBaseFolderMenuItem>().ToList())
         {
             RecursivelyResetUnreadItemCount(subMenuItem);
         }
@@ -128,7 +154,9 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
 
     public bool TryGetSpecialFolderMenuItem(Guid accountId, SpecialFolderType specialFolderType, out FolderMenuItem value)
     {
-        value = this.OfType<IBaseFolderMenuItem>()
+        var rootItems = this.ToList();
+
+        value = rootItems.OfType<IBaseFolderMenuItem>()
                 .FirstOrDefault(a => a.HandlingFolders.Any(b => b.MailAccountId == accountId && b.SpecialFolderType == specialFolderType)) as FolderMenuItem;
 
         return value != null;
@@ -142,11 +170,12 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
     public AccountMenuItem GetSpecificAccountMenuItem(Guid accountId)
     {
         AccountMenuItem accountMenuItem = null;
+        var rootItems = this.ToList();
 
-        accountMenuItem = this.OfType<AccountMenuItem>().FirstOrDefault(a => a.HoldingAccounts.Any(b => b.Id == accountId));
+        accountMenuItem = rootItems.OfType<AccountMenuItem>().FirstOrDefault(a => a.HoldingAccounts.Any(b => b.Id == accountId));
 
         // Look for the items inside the merged accounts if regular menu item is not found.
-        accountMenuItem ??= this.OfType<MergedAccountMenuItem>()
+        accountMenuItem ??= rootItems.OfType<MergedAccountMenuItem>()
             .FirstOrDefault(a => a.HoldingAccounts.Any(b => b.Id == accountId))?.SubMenuItems
             .OfType<AccountMenuItem>()
             .FirstOrDefault(a => a.AccountId == accountId);
@@ -167,7 +196,7 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
     /// <param name="isEnabled">Whether menu items should be enabled or disabled.</param>
     public async Task SetAccountMenuItemEnabledStatusAsync(bool isEnabled)
     {
-        var accountItems = this.Where(a => a is IAccountMenuItem).Cast<IAccountMenuItem>();
+        var accountItems = this.Where(a => a is IAccountMenuItem).Cast<IAccountMenuItem>().ToList();
 
         await _dispatcher.ExecuteOnUIThread(() =>
         {
@@ -192,6 +221,7 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
     {
         // Check root-level items.
         var rootItem = this.OfType<IBaseFolderMenuItem>()
+            .Where(a => a is not IMailCategoryMenuItem && a is not IMergedMailCategoryMenuItem)
             .FirstOrDefault(a => a.HandlingFolders.Any(b => b.Id == folderId));
 
         if (rootItem != null)
@@ -201,7 +231,7 @@ public class MenuItemCollection : ObservableRangeCollection<IMenuItem>
         }
 
         // Check sub-items of root folders.
-        foreach (var rootFolder in this.OfType<IBaseFolderMenuItem>())
+        foreach (var rootFolder in this.OfType<IBaseFolderMenuItem>().ToList())
         {
             var subItem = rootFolder.SubMenuItems
                 .OfType<IBaseFolderMenuItem>()

Wino.Core.Domain/MenuItems/MergedMailCategoryMenuItem.cs

@@ -0,0 +1,44 @@
+using System.Collections.Generic;
+using System.Linq;
+using CommunityToolkit.Mvvm.ComponentModel;
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Entities.Shared;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Interfaces;
+using Wino.Core.Domain.Models.Folders;
+
+namespace Wino.Core.Domain.MenuItems;
+
+public partial class MergedMailCategoryMenuItem : MenuItemBase<List<MailCategory>, IMenuItem>, IMergedAccountFolderMenuItem, IMergedMailCategoryMenuItem
+{
+    private readonly IReadOnlyList<IMailItemFolder> _handlingFolders;
+
+    [ObservableProperty]
+    private int unreadItemCount;
+
+    public MergedMailCategoryMenuItem(List<MailCategory> categories, IEnumerable<IMailItemFolder> handlingFolders, MergedInbox mergedInbox)
+        : base(categories, null, null)
+    {
+        _handlingFolders = handlingFolders?.ToList() ?? [];
+        MergedInbox = mergedInbox;
+    }
+
+    public string FolderName => Parameter.FirstOrDefault()?.Name ?? string.Empty;
+    public bool IsSynchronizationEnabled => false;
+    public SpecialFolderType SpecialFolderType => SpecialFolderType.Other;
+    public IEnumerable<IMailItemFolder> HandlingFolders => _handlingFolders;
+    public bool IsMoveTarget => true;
+    public bool IsSticky => false;
+    public bool IsSystemFolder => false;
+    public bool ShowUnreadCount => true;
+    public string AssignedAccountName => MergedInbox?.Name;
+    public MergedInbox MergedInbox { get; }
+    public string TextColorHex => Parameter.FirstOrDefault()?.TextColorHex;
+    public string BackgroundColorHex => Parameter.FirstOrDefault()?.BackgroundColorHex;
+    public bool HasTextColor => !string.IsNullOrWhiteSpace(TextColorHex);
+    public IReadOnlyList<MailCategory> Categories => Parameter;
+
+    public void UpdateFolder(IMailItemFolder folder)
+    {
+    }
+}

Wino.Core.Domain/Models/Accounts/UnreadCategoryCountResult.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace Wino.Core.Domain.Models.Accounts;
+
+public class UnreadCategoryCountResult
+{
+    public Guid CategoryId { get; set; }
+    public Guid AccountId { get; set; }
+    public int UnreadItemCount { get; set; }
+}

Wino.Core.Domain/Models/Calendar/CalendarPageNavigationArgs.cs

@@ -1,4 +1,5 @@
-using System;
+#nullable enable
+using System;
 
 namespace Wino.Core.Domain.Models.Calendar;
 
@@ -18,4 +19,9 @@ public class CalendarPageNavigationArgs
     /// Force reloading the calendar data even when the target range does not change.
     /// </summary>
     public bool ForceReload { get; set; }
+
+    /// <summary>
+    /// Optional event target to navigate to after the calendar page loads the requested range.
+    /// </summary>
+    public CalendarItemTarget? PendingTarget { get; set; }
 }

Wino.Core.Domain/Models/MailItem/MailCategoryColorOption.cs

@@ -0,0 +1,3 @@
+namespace Wino.Core.Domain.Models.MailItem;
+
+public sealed record MailCategoryColorOption(string BackgroundColorHex, string TextColorHex);

Wino.Core.Domain/Models/MailItem/MailCategoryDialogResult.cs

@@ -0,0 +1,3 @@
+namespace Wino.Core.Domain.Models.MailItem;
+
+public sealed record MailCategoryDialogResult(string Name, string BackgroundColorHex, string TextColorHex);

Wino.Core.Domain/Models/MailItem/MailCategoryPalette.cs

@@ -0,0 +1,30 @@
+using System.Collections.Generic;
+
+namespace Wino.Core.Domain.Models.MailItem;
+
+public static class MailCategoryPalette
+{
+    public static IReadOnlyList<MailCategoryColorOption> DefaultOptions { get; } =
+    [
+        new("#FEE2E2", "#991B1B"),
+        new("#FECACA", "#7F1D1D"),
+        new("#FFEDD5", "#9A3412"),
+        new("#FED7AA", "#7C2D12"),
+        new("#FEF3C7", "#92400E"),
+        new("#FDE68A", "#78350F"),
+        new("#ECFCCB", "#3F6212"),
+        new("#D9F99D", "#365314"),
+        new("#DCFCE7", "#166534"),
+        new("#BBF7D0", "#14532D"),
+        new("#CCFBF1", "#115E59"),
+        new("#99F6E4", "#134E4A"),
+        new("#CFFAFE", "#155E75"),
+        new("#A5F3FC", "#164E63"),
+        new("#DBEAFE", "#1D4ED8"),
+        new("#BFDBFE", "#1E3A8A"),
+        new("#E0E7FF", "#4338CA"),
+        new("#DDD6FE", "#5B21B6"),
+        new("#F3E8FF", "#7E22CE"),
+        new("#FCE7F3", "#9D174D")
+    ];
+}

Wino.Core.Domain/Models/MailItem/MailInsertPackage.cs

@@ -9,4 +9,5 @@ public record NewMailItemPackage(
     MailCopy Copy,
     MimeMessage Mime,
     string AssignedRemoteFolderId,
-    IReadOnlyList<AccountContact> ExtractedContacts = null);
+    IReadOnlyList<AccountContact> ExtractedContacts = null,
+    IReadOnlyList<string> CategoryNames = null);

Wino.Core.Domain/Models/MailItem/MailListInitializationOptions.cs

@@ -17,4 +17,8 @@ public record MailListInitializationOptions(IEnumerable<IMailItemFolder> Folders
                                             List<MailCopy> PreFetchMailCopies = null,
                                             bool DeduplicateByServerId = false,
                                             int Skip = 0,
-                                            int Take = 0);
+                                            int Take = 0)
+{
+    public IReadOnlyList<Guid> CategoryIds { get; init; }
+    public bool IsCategoryView => CategoryIds?.Count > 0;
+}

Wino.Core.Domain/Models/Requests/RequestBase.cs

@@ -35,6 +35,10 @@ public abstract record CalendarRequestBase(CalendarItem Item) : RequestBase<Cale
     public virtual Guid? LocalCalendarItemId => Item?.Id;
 }
 
+public abstract record CategoryRequestBase(Guid AccountId) : RequestBase<CategorySynchronizerOperation>, ICategoryActionRequest
+{
+}
+
 public class BatchCollection<TRequestType> : List<TRequestType>, IUIChangeRequest where TRequestType : IUIChangeRequest
 {
     public BatchCollection(IEnumerable<TRequestType> collection) : base(collection)

Wino.Core.Domain/Models/Settings/SettingsNavigationItemInfo.cs

@@ -68,6 +68,11 @@ public static class SettingsNavigationInfoProvider
                 Translator.SettingsMessageList_Description,
                 "\uE8C4",
                 searchKeywords: Translator.SettingsSearch_MessageList_Keywords),
+            new(WinoPage.MailNotificationSettingsPage,
+                Translator.SettingsMailNotifications_Title,
+                Translator.SettingsMailNotifications_Description,
+                "\uE7F4",
+                searchKeywords: Translator.SettingsSearch_MailNotifications_Keywords),
             new(WinoPage.ReadComposePanePage,
                 Translator.SettingsReadComposePane_Title,
                 Translator.SettingsReadComposePane_Description,
@@ -149,6 +154,7 @@ public static class SettingsNavigationInfoProvider
             WinoPage.PersonalizationPage => Translator.SettingsPersonalization_Title,
             WinoPage.AboutPage => Translator.SettingsAbout_Title,
             WinoPage.MessageListPage => Translator.SettingsMessageList_Title,
+            WinoPage.MailNotificationSettingsPage => Translator.SettingsMailNotifications_Title,
             WinoPage.ReadComposePanePage => Translator.SettingsReadComposePane_Title,
             WinoPage.AppPreferencesPage => Translator.SettingsAppPreferences_Title,
             WinoPage.CalendarSettingsPage => Translator.CalendarSettings_Preferences_Title,
@@ -170,6 +176,7 @@ public static class SettingsNavigationInfoProvider
             WinoPage.AccountDetailsPage => WinoPage.ManageAccountsPage,
             WinoPage.MergedAccountDetailsPage => WinoPage.ManageAccountsPage,
             WinoPage.AliasManagementPage => WinoPage.ManageAccountsPage,
+            WinoPage.MailCategoryManagementPage => WinoPage.ManageAccountsPage,
             WinoPage.SignatureManagementPage => WinoPage.ManageAccountsPage,
             WinoPage.ImapCalDavSettingsPage => WinoPage.ManageAccountsPage,
             WinoPage.CreateEmailTemplatePage => WinoPage.EmailTemplatesPage,

Wino.Core.Domain/Translations/en_US/resources.json

@@ -67,6 +67,7 @@
     "BasicIMAPSetupDialog_Password": "Password",
     "BasicIMAPSetupDialog_Title": "IMAP Account",
     "Busy": "Busy",
+    "Buttons_Add": "Add",
     "Buttons_AddAccount": "Add Account",
     "Buttons_FixAccount": "Fix Account",
     "Buttons_AddNewAlias": "Add New Alias",
@@ -83,6 +84,7 @@
     "Buttons_Delete": "Delete",
     "Buttons_Deny": "Deny",
     "Buttons_Discard": "Discard",
+    "Buttons_Dismiss": "Dismiss",
     "Buttons_Edit": "Edit",
     "Buttons_EnableImageRendering": "Enable",
     "Buttons_Multiselect": "Select Multiple",
@@ -213,6 +215,8 @@
     "CalendarEventDetails_Organizer": "Organizer",
     "CalendarEventDetails_People": "People",
     "CalendarEventDetails_ReadOnlyEvent": "Read-only event",
+    "CalendarReadOnly_Title": "Read-only calendar",
+    "CalendarReadOnly_Message": "You can't update this calendar or its events. This calendar is read-only.",
     "CalendarContextMenu_Respond": "Respond",
     "CalendarEventDetails_Reminder": "Reminder",
     "CalendarReminder_StartedHoursAgo": "Started {0} hours ago",
@@ -875,10 +879,28 @@
     "SettingsManageAccountSettings_Title": "Manage Accounts",
     "SettingsManageAliases_Description": "See e-mail aliases assigned for this account, update or delete them.",
     "SettingsManageAliases_Title": "Aliases",
+    "SettingsMailCategories_Description": "Manage synchronized and local categories for this account.",
+    "SettingsMailCategories_Title": "Categories",
     "SettingsEditAccountDetails_Title": "Edit Account Details",
     "SettingsEditAccountDetails_Description": "Change account name, sender name and assign a new color if you like.",
     "EditAccountDetailsPage_SaveSuccess_Title": "Changes Saved",
     "EditAccountDetailsPage_SaveSuccess_Message": "Your account details have been updated successfully.",
+    "MailCategoryManagementPage_Title": "Categories",
+    "MailCategoryManagementPage_Description": "Create, edit, delete, and favorite categories for this account.",
+    "MailCategoryManagementPage_Empty": "No categories yet.",
+    "MailCategoryManagementPage_DeleteConfirmationTitle": "Delete Category",
+    "MailCategoryManagementPage_DeleteConfirmationMessage": "Delete category \"{0}\"?",
+    "MailCategoryManagementPage_RefreshConfirmationMessage": "This will delete all your local categories, and re-synchronize everything from the server. Do you want to continue?",
+    "MailCategoryMenuItem": "Category",
+    "MailCategoryDialog_CreateTitle": "Create category",
+    "MailCategoryDialog_EditTitle": "Edit category",
+    "MailCategoryDialog_Name": "Name",
+    "MailCategoryDialog_NamePlaceholder": "Category name",
+    "MailCategoryDialog_Color": "Color",
+    "MailCategoryDialog_InvalidNameTitle": "Category name required",
+    "MailCategoryDialog_InvalidNameMessage": "Enter a category name to continue.",
+    "MailCategoryDialog_DuplicateTitle": "Category already exists",
+    "MailCategoryDialog_DuplicateMessage": "A category with the same name already exists for this account.",
     "SettingsManageLink_Description": "Move items to add new link or remove existing link.",
     "SettingsManageLink_Title": "Manage Link",
     "SettingsMarkAsRead_Description": "Change what should happen to the selected item.",
@@ -889,6 +911,14 @@
     "SettingsMarkAsRead_WhenSelected": "When selected",
     "SettingsMessageList_Description": "Change how your messages should be organized in mail list.",
     "SettingsMessageList_Title": "Message List",
+    "SettingsMailNotifications_Title": "Notifications",
+    "SettingsMailNotifications_Description": "Notification settings and preferences for mails.",
+    "SettingsMailNotifications_Actions_Title": "App notification actions.",
+    "SettingsMailNotifications_Actions_Description": "Customize the button behaviors on the notifications as you like.",
+    "SettingsMailNotifications_FirstAction_Title": "First notification action",
+    "SettingsMailNotifications_FirstAction_Description": "Choose the first button shown on mail notifications.",
+    "SettingsMailNotifications_SecondAction_Title": "Second notification action",
+    "SettingsMailNotifications_SecondAction_Description": "Choose the second button shown on mail notifications.",
     "SettingsNoAccountSetupMessage": "You didn't setup any accounts yet.",
     "SettingsNotifications_Description": "Turn on or off notifications for this account.",
     "SettingsNotifications_Title": "Notifications",
@@ -925,6 +955,7 @@
     "SettingsSearch_About_Keywords": "about;version;website;privacy;github;donate;store;support",
     "SettingsSearch_KeyboardShortcuts_Keywords": "shortcut;shortcuts;hotkey;hotkeys;keyboard;keys",
     "SettingsSearch_MessageList_Keywords": "message;messages;list;threading;threads;avatar;preview;sender",
+    "SettingsSearch_MailNotifications_Keywords": "mail;notification;notifications;toast;action;actions;reply;reply all;forward;archive;delete;junk;read",
     "SettingsSearch_ReadComposePane_Keywords": "reader;compose;composer;font;fonts;external content;display;reading",
     "SettingsSearch_SignatureAndEncryption_Keywords": "signature;signatures;encryption;certificate;certificates;s mime;smime;security",
     "SettingsSearch_Storage_Keywords": "storage;cache;caching;mime;disk;space;cleanup;clean up;local data",
@@ -1491,11 +1522,13 @@
     "AccountSetup_Step_TestingCalendarAuth": "Testing calendar authentication",
     "AccountSetup_Step_SavingAccount": "Saving account information",
     "AccountSetup_Step_FetchingCalendarMetadata": "Fetching calendar metadata",
+    "AccountSetup_Step_SyncingCategories": "Synchronizing categories",
     "AccountSetup_Step_SyncingAliases": "Synchronizing aliases",
     "AccountSetup_Step_Finalizing": "Finalizing setup",
     "AccountSetup_FailureMessage": "Setup failed. Go back to fix your settings, or try again later.",
     "AccountSetup_SuccessMessage": "Your account has been set up successfully!",
     "AccountSetup_GoBackButton": "Go Back",
     "AccountSetup_TryAgainButton": "Try Again",
+    "Exception_FailedToSynchronizeCategories": "Failed to synchronize categories",
     "ImapCalDavSettings_AutoDiscoveryFailed": "Auto-discovery failed. Please enter settings manually in the Advanced tab."
 }

Wino.Core.Tests/Services/MailFetchingTests.cs

@@ -510,7 +510,8 @@ public class MailFetchingTests : IAsyncLifetime
             preferencesService.Object,
             contactPictureFileService.Object);
 
-        var folderService = new FolderService(db, accountService);
+        var mailCategoryService = new MailCategoryService(db);
+        var folderService = new FolderService(db, accountService, mailCategoryService);
         var contactService = new ContactService(db);
         var sentMailReceiptService = new SentMailReceiptService(db, folderService, accountService);
 
@@ -522,6 +523,7 @@ public class MailFetchingTests : IAsyncLifetime
             signatureService.Object,
             mimeFileService.Object,
             preferencesService.Object,
-            sentMailReceiptService);
+            sentMailReceiptService,
+            mailCategoryService);
     }
 }

Wino.Core.Tests/Services/MailThreadingTests.cs

@@ -269,7 +269,8 @@ public class MailThreadingTests : IAsyncLifetime
             preferencesService.Object,
             contactPictureFileService.Object);
 
-        var folderService = new FolderService(db, accountService);
+        var mailCategoryService = new MailCategoryService(db);
+        var folderService = new FolderService(db, accountService, mailCategoryService);
         var contactService = new ContactService(db);
         var sentMailReceiptService = new SentMailReceiptService(db, folderService, accountService);
 
@@ -281,6 +282,7 @@ public class MailThreadingTests : IAsyncLifetime
             signatureService.Object,
             mimeFileService.Object,
             preferencesService.Object,
-            sentMailReceiptService);
+            sentMailReceiptService,
+            mailCategoryService);
     }
 }

Wino.Core.Tests/Synchronizers/OutlookSynchronizerRequestSuccessTests.cs

@@ -70,8 +70,9 @@ public sealed class OutlookSynchronizerRequestSuccessTests
 
         var authenticator = new Mock<IAuthenticator>(MockBehavior.Loose);
         var errorFactory = new Mock<IOutlookSynchronizerErrorHandlerFactory>(MockBehavior.Loose);
+        var mailCategoryService = new Mock<IMailCategoryService>(MockBehavior.Loose);
 
-        return new OutlookSynchronizer(account, authenticator.Object, changeProcessor, errorFactory.Object);
+        return new OutlookSynchronizer(account, authenticator.Object, changeProcessor, errorFactory.Object, mailCategoryService.Object);
     }
 
     private static MailCopy CreateMailCopy() =>

Wino.Core/Extensions/GoogleIntegratorExtensions.cs

@@ -14,27 +14,32 @@ namespace Wino.Core.Extensions;
 
 public static class GoogleIntegratorExtensions
 {
-    private static string GetNormalizedLabelName(string labelName)
+    private static bool TryGetKnownFolderLabelName(string labelName, out string normalizedLabelName)
     {
-        // 1. Remove CATEGORY_ prefix.
+        normalizedLabelName = string.Empty;
-        var normalizedLabelName = labelName.Replace(ServiceConstants.CATEGORY_PREFIX, string.Empty);
 
-        // 2. Normalize label name by capitalizing first letter.
+        if (string.IsNullOrEmpty(labelName))
-        normalizedLabelName = char.ToUpper(normalizedLabelName[0]) + normalizedLabelName.Substring(1).ToLower();
+            return false;
 
-        return normalizedLabelName;
+        var knownFolderKey = labelName.Replace(ServiceConstants.CATEGORY_PREFIX, string.Empty);
+
+        if (!ServiceConstants.KnownFolderDictionary.ContainsKey(knownFolderKey))
+            return false;
+
+        normalizedLabelName = char.ToUpper(knownFolderKey[0]) + knownFolderKey.Substring(1).ToLower();
+
+        return true;
     }
 
     public static MailItemFolder GetLocalFolder(this Label label, ListLabelsResponse labelsResponse, Guid accountId)
     {
-        var normalizedLabelName = GetFolderName(label.Name);
+        var folderName = GetFolderName(label.Name);
 
-        // Even though we normalize the label name, check is done by capitalizing the label name.
+        var lookupLabelName = GetLookupLabelName(label.Name);
-        var capitalNormalizedLabelName = normalizedLabelName.ToUpper();
 
-        bool isSpecialFolder = ServiceConstants.KnownFolderDictionary.ContainsKey(capitalNormalizedLabelName);
+        bool isSpecialFolder = ServiceConstants.KnownFolderDictionary.ContainsKey(lookupLabelName);
 
-        var specialFolderType = isSpecialFolder ? ServiceConstants.KnownFolderDictionary[capitalNormalizedLabelName] : SpecialFolderType.Other;
+        var specialFolderType = isSpecialFolder ? ServiceConstants.KnownFolderDictionary[lookupLabelName] : SpecialFolderType.Other;
 
         // We used to support FOLDER_HIDE_IDENTIFIER to hide invisible folders.
         // However, a lot of people complained that they don't see their folders after the initial sync
@@ -59,7 +64,7 @@ public static class GoogleIntegratorExtensions
         {
             TextColorHex = label.Color?.TextColor,
             BackgroundColorHex = label.Color?.BackgroundColor,
-            FolderName = normalizedLabelName,
+            FolderName = folderName,
             RemoteFolderId = label.Id,
             Id = Guid.NewGuid(),
             MailAccountId = accountId,
@@ -104,7 +109,29 @@ public static class GoogleIntegratorExtensions
         return labelsResponse.Labels.FirstOrDefault(a => a.Name == parentLabelName)?.Id ?? string.Empty;
     }
 
+    public static string GetLookupLabelName(string fullFolderName)
+    {
+        var folderName = GetLastFolderName(fullFolderName);
+
+        if (string.IsNullOrEmpty(folderName))
+            return string.Empty;
+
+        return folderName.Replace(ServiceConstants.CATEGORY_PREFIX, string.Empty);
+    }
+
     public static string GetFolderName(string fullFolderName)
+    {
+        var lastPart = GetLastFolderName(fullFolderName);
+
+        if (string.IsNullOrEmpty(lastPart))
+            return string.Empty;
+
+        return TryGetKnownFolderLabelName(lastPart, out var normalizedLabelName)
+            ? normalizedLabelName
+            : lastPart;
+    }
+
+    private static string GetLastFolderName(string fullFolderName)
     {
         if (string.IsNullOrEmpty(fullFolderName)) return string.Empty;
 
@@ -113,9 +140,7 @@ public static class GoogleIntegratorExtensions
 
         string[] parts = fullFolderName.Split(ServiceConstants.FOLDER_SEPERATOR_CHAR);
 
-        var lastPart = parts[parts.Length - 1];
+        return parts[parts.Length - 1];
-
-        return GetNormalizedLabelName(lastPart);
     }
 
     public static List<RemoteAccountAlias> GetRemoteAliases(this ListSendAsResponse response)
@@ -145,6 +170,8 @@ public static class GoogleIntegratorExtensions
             Id = Guid.NewGuid(),
             TimeZone = calendarListEntry.TimeZone,
             IsPrimary = calendarListEntry.Primary.GetValueOrDefault(),
+            IsReadOnly = !string.Equals(calendarListEntry.AccessRole, "owner", StringComparison.OrdinalIgnoreCase)
+                         && !string.Equals(calendarListEntry.AccessRole, "writer", StringComparison.OrdinalIgnoreCase),
             IsSynchronizationEnabled = true,
         };
 

Wino.Core/Extensions/OutlookIntegratorExtensions.cs

@@ -190,6 +190,7 @@ public static class OutlookIntegratorExtensions
             Id = Guid.NewGuid(),
             RemoteCalendarId = outlookCalendar.Id,
             IsPrimary = outlookCalendar.IsDefaultCalendar.GetValueOrDefault(),
+            IsReadOnly = !outlookCalendar.CanEdit.GetValueOrDefault(true),
             Name = outlookCalendar.Name,
             IsSynchronizationEnabled = true,
             IsExtended = true,

Wino.Core/Requests/Category/MailCategoryCreateRequest.cs

@@ -0,0 +1,10 @@
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Models.Requests;
+
+namespace Wino.Core.Requests.Category;
+
+public record MailCategoryCreateRequest(MailCategory Category) : CategoryRequestBase(Category.MailAccountId)
+{
+    public override CategorySynchronizerOperation Operation => CategorySynchronizerOperation.CreateCategory;
+}

Wino.Core/Requests/Category/MailCategoryDeleteRequest.cs

@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Models.Requests;
+
+namespace Wino.Core.Requests.Category;
+
+public record MailCategoryDeleteRequest(
+    MailCategory Category,
+    string PreviousRemoteId,
+    IReadOnlyList<MailCategoryMessageUpdateTarget> AffectedMessages = null) : CategoryRequestBase(Category.MailAccountId)
+{
+    public override CategorySynchronizerOperation Operation => CategorySynchronizerOperation.DeleteCategory;
+}

Wino.Core/Requests/Category/MailCategoryRequestModels.cs

@@ -0,0 +1,5 @@
+using System.Collections.Generic;
+
+namespace Wino.Core.Requests.Category;
+
+public sealed record MailCategoryMessageUpdateTarget(string MessageId, IReadOnlyList<string> CategoryNames);

Wino.Core/Requests/Category/MailCategoryUpdateRequest.cs

@@ -0,0 +1,15 @@
+using System.Collections.Generic;
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Models.Requests;
+
+namespace Wino.Core.Requests.Category;
+
+public record MailCategoryUpdateRequest(
+    MailCategory Category,
+    string PreviousName,
+    string PreviousRemoteId,
+    IReadOnlyList<MailCategoryMessageUpdateTarget> AffectedMessages = null) : CategoryRequestBase(Category.MailAccountId)
+{
+    public override CategorySynchronizerOperation Operation => CategorySynchronizerOperation.UpdateCategory;
+}

Wino.Core/Requests/Mail/MailCategoryAssignmentRequest.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Collections.Generic;
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Interfaces;
+using Wino.Core.Domain.Models.Requests;
+
+namespace Wino.Core.Requests.Mail;
+
+public record MailCategoryAssignmentRequest(
+    MailCopy Item,
+    Guid MailCategoryId,
+    string CategoryName,
+    IReadOnlyList<string> CategoryNames,
+    bool IsAssigned) : MailRequestBase(Item), ICustomFolderSynchronizationRequest
+{
+    public override MailSynchronizerOperation Operation => MailSynchronizerOperation.UpdateCategories;
+    public List<Guid> SynchronizationFolderIds => [Item.FolderId];
+    public bool ExcludeMustHaveFolders => true;
+}
+
+public class BatchMailCategoryAssignmentRequest : BatchCollection<MailCategoryAssignmentRequest>
+{
+    public BatchMailCategoryAssignmentRequest(IEnumerable<MailCategoryAssignmentRequest> collection) : base(collection)
+    {
+    }
+}

Wino.Core/Services/SynchronizationManager.cs

@@ -370,6 +370,26 @@ public class SynchronizationManager : ISynchronizationManager, IRecipient<Accoun
         return await SynchronizeMailAsync(options, cancellationToken);
     }
 
+    /// <summary>
+    /// Handles category synchronization for the given account.
+    /// </summary>
+    /// <param name="accountId">Account ID to synchronize categories for</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Synchronization result</returns>
+    public async Task<MailSynchronizationResult> SynchronizeCategoriesAsync(Guid accountId,
+                                                                            CancellationToken cancellationToken = default)
+    {
+        EnsureInitialized();
+
+        var options = new MailSynchronizationOptions
+        {
+            AccountId = accountId,
+            Type = MailSynchronizationType.Categories
+        };
+
+        return await SynchronizeMailAsync(options, cancellationToken);
+    }
+
     /// <summary>
     /// Handles profile synchronization for the given account.
     /// </summary>

Wino.Core/Services/SynchronizerFactory.cs

@@ -26,6 +26,7 @@ public class SynchronizerFactory : ISynchronizerFactory
     private readonly ICalDavClient _calDavClient;
     private readonly IAutoDiscoveryService _autoDiscoveryService;
     private readonly ICalendarService _calendarService;
+    private readonly IMailCategoryService _mailCategoryService;
 
     private readonly List<IWinoSynchronizerBase> synchronizerCache = new();
 
@@ -41,7 +42,8 @@ public class SynchronizerFactory : ISynchronizerFactory
                                UnifiedImapSynchronizer unifiedImapSynchronizer,
                                ICalDavClient calDavClient,
                                IAutoDiscoveryService autoDiscoveryService,
-                               ICalendarService calendarService)
+                               ICalendarService calendarService,
+                               IMailCategoryService mailCategoryService)
     {
         _outlookChangeProcessor = outlookChangeProcessor;
         _gmailChangeProcessor = gmailChangeProcessor;
@@ -56,6 +58,7 @@ public class SynchronizerFactory : ISynchronizerFactory
         _calDavClient = calDavClient;
         _autoDiscoveryService = autoDiscoveryService;
         _calendarService = calendarService;
+        _mailCategoryService = mailCategoryService;
     }
 
     public async Task<IWinoSynchronizerBase> GetAccountSynchronizerAsync(Guid accountId)
@@ -86,7 +89,7 @@ public class SynchronizerFactory : ISynchronizerFactory
         {
             case Domain.Enums.MailProviderType.Outlook:
                 var outlookAuthenticator = _authenticationProvider.GetAuthenticator(Domain.Enums.MailProviderType.Outlook) as IOutlookAuthenticator;
-                return new OutlookSynchronizer(mailAccount, outlookAuthenticator, _outlookChangeProcessor, _outlookSynchronizerErrorHandlerFactory);
+                return new OutlookSynchronizer(mailAccount, outlookAuthenticator, _outlookChangeProcessor, _outlookSynchronizerErrorHandlerFactory, _mailCategoryService);
             case Domain.Enums.MailProviderType.Gmail:
                 var gmailAuthenticator = _authenticationProvider.GetAuthenticator(Domain.Enums.MailProviderType.Gmail) as IGmailAuthenticator;
                 return new GmailSynchronizer(mailAccount, gmailAuthenticator, _gmailChangeProcessor, _gmailSynchronizerErrorHandlerFactory);

Wino.Core/Services/WinoRequestDelegator.cs

@@ -165,6 +165,13 @@ public class WinoRequestDelegator : IWinoRequestDelegator
         if (calendarPreparationRequest == null)
             return;
 
+        var resolvedCalendar = await ResolveCalendarAsync(calendarPreparationRequest).ConfigureAwait(false);
+        if (resolvedCalendar?.IsReadOnly == true)
+        {
+            _dialogService.ShowReadOnlyCalendarMessage();
+            return;
+        }
+
         IRequestBase request = calendarPreparationRequest.Operation switch
         {
             CalendarSynchronizerOperation.CreateEvent => await CreateCalendarEventRequestAsync(calendarPreparationRequest).ConfigureAwait(false),
@@ -200,6 +207,21 @@ public class WinoRequestDelegator : IWinoRequestDelegator
         await QueueCalendarSynchronizationAsync(accountId);
     }
 
+    public async Task ExecuteAsync(Guid accountId, IEnumerable<IRequestBase> requests)
+    {
+        var requestList = requests?.Where(a => a != null).ToList() ?? [];
+        if (requestList.Count == 0)
+            return;
+
+        foreach (var request in requestList)
+        {
+            await QueueRequestAsync(request, accountId).ConfigureAwait(false);
+        }
+
+        await SendSyncActionsAddedAsync(requestList, accountId).ConfigureAwait(false);
+        await QueueSynchronizationAsync(accountId).ConfigureAwait(false);
+    }
+
     private async Task<IRequestBase> CreateCalendarEventRequestAsync(CalendarOperationPreparationRequest calendarPreparationRequest)
     {
         var composeResult = calendarPreparationRequest.ComposeResult
@@ -212,6 +234,25 @@ public class WinoRequestDelegator : IWinoRequestDelegator
         return new CreateCalendarEventRequest(composeResult, assignedCalendar);
     }
 
+    private async Task<AccountCalendar> ResolveCalendarAsync(CalendarOperationPreparationRequest calendarPreparationRequest)
+    {
+        if (calendarPreparationRequest.Operation == CalendarSynchronizerOperation.CreateEvent)
+        {
+            var calendarId = calendarPreparationRequest.ComposeResult?.CalendarId ?? Guid.Empty;
+            return calendarId == Guid.Empty
+                ? null
+                : await _calendarService.GetAccountCalendarAsync(calendarId).ConfigureAwait(false);
+        }
+
+        if (calendarPreparationRequest.CalendarItem?.AssignedCalendar is AccountCalendar assignedCalendar)
+            return assignedCalendar;
+
+        var fallbackCalendarId = calendarPreparationRequest.CalendarItem?.CalendarId ?? Guid.Empty;
+        return fallbackCalendarId == Guid.Empty
+            ? null
+            : await _calendarService.GetAccountCalendarAsync(fallbackCalendarId).ConfigureAwait(false);
+    }
+
     private IRequestBase CreateDeclineRequest(CalendarItem calendarItem, string responseMessage)
     {
         // For Outlook accounts, declined events are deleted by the server after synchronization.

Wino.Core/Synchronizers/GmailSynchronizer.cs

@@ -759,6 +759,8 @@ public class GmailSynchronizer : WinoSynchronizer<IClientServiceRequest, Message
                     existingLocalCalendar.BackgroundColorHex = resolvedColor;
                     existingLocalCalendar.TextColorHex = ColorHelpers.GetReadableTextColorHex(existingLocalCalendar.BackgroundColorHex);
                     existingLocalCalendar.IsPrimary = string.Equals(existingLocalCalendar.RemoteCalendarId, remotePrimaryCalendarId, StringComparison.OrdinalIgnoreCase);
+                    existingLocalCalendar.IsReadOnly = !string.Equals(calendar.AccessRole, "owner", StringComparison.OrdinalIgnoreCase)
+                                                      && !string.Equals(calendar.AccessRole, "writer", StringComparison.OrdinalIgnoreCase);
 
                     updatedCalendars.Add(existingLocalCalendar);
                 }
@@ -902,7 +904,7 @@ public class GmailSynchronizer : WinoSynchronizer<IClientServiceRequest, Message
 
                 if (ShouldUpdateFolder(remoteFolder, existingLocalFolder))
                 {
-                    existingLocalFolder.FolderName = remoteFolder.Name;
+                    existingLocalFolder.FolderName = GoogleIntegratorExtensions.GetFolderName(remoteFolder.Name);
                     existingLocalFolder.TextColorHex = remoteFolder.Color?.TextColor;
                     existingLocalFolder.BackgroundColorHex = remoteFolder.Color?.BackgroundColor;
 
@@ -940,14 +942,17 @@ public class GmailSynchronizer : WinoSynchronizer<IClientServiceRequest, Message
         var remoteBackgroundColor = ResolveSynchronizedCalendarBackgroundColor(GetRemoteGmailCalendarBackgroundColor(calendarListEntry), accountCalendar);
         var remoteTextColor = ColorHelpers.GetReadableTextColorHex(remoteBackgroundColor);
         var remoteIsPrimary = string.Equals(calendarListEntry.Id, remotePrimaryCalendarId, StringComparison.OrdinalIgnoreCase);
+        var remoteIsReadOnly = !string.Equals(calendarListEntry.AccessRole, "owner", StringComparison.OrdinalIgnoreCase)
+                               && !string.Equals(calendarListEntry.AccessRole, "writer", StringComparison.OrdinalIgnoreCase);
 
         bool isNameChanged = !string.Equals(accountCalendar.Name, remoteCalendarName, StringComparison.OrdinalIgnoreCase);
         bool isTimeZoneChanged = !string.Equals(accountCalendar.TimeZone, remoteTimeZone, StringComparison.OrdinalIgnoreCase);
         bool isBackgroundColorChanged = !string.Equals(accountCalendar.BackgroundColorHex, remoteBackgroundColor, StringComparison.OrdinalIgnoreCase);
         bool isTextColorChanged = !string.Equals(accountCalendar.TextColorHex, remoteTextColor, StringComparison.OrdinalIgnoreCase);
         bool isPrimaryChanged = accountCalendar.IsPrimary != remoteIsPrimary;
+        bool isReadOnlyChanged = accountCalendar.IsReadOnly != remoteIsReadOnly;
 
-        return isNameChanged || isTimeZoneChanged || isBackgroundColorChanged || isTextColorChanged || isPrimaryChanged;
+        return isNameChanged || isTimeZoneChanged || isBackgroundColorChanged || isTextColorChanged || isPrimaryChanged || isReadOnlyChanged;
     }
 
     private static string GetRemoteGmailCalendarBackgroundColor(CalendarListEntry calendarListEntry)
@@ -993,9 +998,9 @@ public class GmailSynchronizer : WinoSynchronizer<IClientServiceRequest, Message
     private bool ShouldUpdateFolder(Label remoteFolder, MailItemFolder existingLocalFolder)
     {
         var remoteFolderName = GoogleIntegratorExtensions.GetFolderName(remoteFolder.Name);
-        var localFolderName = GoogleIntegratorExtensions.GetFolderName(existingLocalFolder.FolderName);
+        var localFolderName = existingLocalFolder.FolderName ?? string.Empty;
 
-        bool isNameChanged = !localFolderName.Equals(remoteFolderName, StringComparison.OrdinalIgnoreCase);
+        bool isNameChanged = !localFolderName.Equals(remoteFolderName, StringComparison.Ordinal);
         bool isColorChanged = existingLocalFolder.BackgroundColorHex != remoteFolder.Color?.BackgroundColor ||
                 existingLocalFolder.TextColorHex != remoteFolder.Color?.TextColor;
 

Wino.Core/Synchronizers/OutlookSynchronizer.cs

@@ -41,6 +41,7 @@ using Wino.Core.Integration.Processors;
 using Wino.Core.Misc;
 using Wino.Core.Requests.Bundles;
 using Wino.Core.Requests.Calendar;
+using Wino.Core.Requests.Category;
 using Wino.Core.Requests.Folder;
 using Wino.Core.Requests.Mail;
 using Wino.Messaging.UI;
@@ -107,6 +108,7 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
         "ParentFolderId",
         "InternetMessageId",
         "InternetMessageHeaders",
+        "Categories",
     ];
 
     private readonly SemaphoreSlim _handleItemRetrievalSemaphore = new(1);
@@ -116,6 +118,7 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
     private readonly IOutlookChangeProcessor _outlookChangeProcessor;
     private readonly GraphServiceClient _graphClient;
     private readonly IOutlookSynchronizerErrorHandlerFactory _errorHandlingFactory;
+    private readonly IMailCategoryService _mailCategoryService;
     private bool _isFolderStructureChanged;
 
     private readonly SemaphoreSlim _concurrentDownloadSemaphore = new(10); // Limit to 10 concurrent downloads
@@ -123,7 +126,8 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
     public OutlookSynchronizer(MailAccount account,
                                IAuthenticator authenticator,
                                IOutlookChangeProcessor outlookChangeProcessor,
-                               IOutlookSynchronizerErrorHandlerFactory errorHandlingFactory) : base(account, WeakReferenceMessenger.Default)
+                               IOutlookSynchronizerErrorHandlerFactory errorHandlingFactory,
+                               IMailCategoryService mailCategoryService) : base(account, WeakReferenceMessenger.Default)
     {
         var tokenProvider = new MicrosoftTokenProvider(Account, authenticator);
 
@@ -138,6 +142,7 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
 
         _outlookChangeProcessor = outlookChangeProcessor;
         _errorHandlingFactory = errorHandlingFactory;
+        _mailCategoryService = mailCategoryService;
     }
 
     #region MS Graph Handlers
@@ -1152,6 +1157,11 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
                     _logger.Debug("Updating flag status for mail {MessageId}: IsFlagged={IsFlagged}", item.Id, isFlagged);
                     await _outlookChangeProcessor.ChangeFlagStatusAsync(item.Id, isFlagged).ConfigureAwait(false);
                 }
+
+                if (item.Categories != null)
+                {
+                    await ReplaceMailAssignmentsAsync(item.Id, item.Categories).ConfigureAwait(false);
+                }
             }
             else
             {
@@ -1208,6 +1218,43 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
         }
     }
 
+    protected override async Task SynchronizeCategoriesAsync(CancellationToken cancellationToken = default)
+    {
+        var response = await _graphClient.Me.Outlook.MasterCategories
+            .GetAsync(cancellationToken: cancellationToken)
+            .ConfigureAwait(false);
+
+        var categories = response?.Value?
+            .Where(a => !string.IsNullOrWhiteSpace(a?.DisplayName))
+            .Select(a =>
+            {
+                var colorOption = GetMailCategoryColorOption(a.Color);
+
+                return new MailCategory
+                {
+                    MailAccountId = Account.Id,
+                    RemoteId = a.Id,
+                    Name = a.DisplayName,
+                    BackgroundColorHex = colorOption.BackgroundColorHex,
+                    TextColorHex = colorOption.TextColorHex,
+                    Source = MailCategorySource.Outlook
+                };
+            })
+            .ToList() ?? [];
+
+        await _mailCategoryService.ReplaceCategoriesAsync(Account.Id, categories).ConfigureAwait(false);
+    }
+
+    private async Task ReplaceMailAssignmentsAsync(string messageId, IEnumerable<string> categoryNames)
+    {
+        var localMailCopies = await _outlookChangeProcessor.GetMailCopiesAsync([messageId]).ConfigureAwait(false);
+
+        foreach (var localMailCopy in localMailCopies)
+        {
+            await _mailCategoryService.ReplaceMailAssignmentsAsync(Account.Id, localMailCopy.UniqueId, categoryNames ?? []).ConfigureAwait(false);
+        }
+    }
+
     private async Task<OutlookSpecialFolderIdInformation> GetSpecialFolderIdsAsync(CancellationToken cancellationToken)
     {
         var localFolders = await _outlookChangeProcessor.GetLocalFoldersAsync(Account.Id).ConfigureAwait(false);
@@ -1767,6 +1814,87 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
         return Move(batchMoveRequest);
     }
 
+    public override List<IRequestBundle<RequestInformation>> UpdateCategories(BatchMailCategoryAssignmentRequest request)
+        => ForEachRequest(request, item => CreateMessageCategoryPatchRequest(item.Item.Id, item.CategoryNames));
+
+    public override List<IRequestBundle<RequestInformation>> CreateCategory(MailCategoryCreateRequest request)
+    {
+        var outlookCategory = new OutlookCategory
+        {
+            DisplayName = request.Category.Name,
+            Color = GetOutlookCategoryColor(request.Category)
+        };
+
+        var requestInfo = _graphClient.Me.Outlook.MasterCategories.ToPostRequestInformation(outlookCategory);
+        return [new HttpRequestBundle<RequestInformation>(requestInfo, request)];
+    }
+
+    public override List<IRequestBundle<RequestInformation>> UpdateCategory(MailCategoryUpdateRequest request)
+    {
+        if (string.IsNullOrWhiteSpace(request.PreviousRemoteId))
+            return CreateCategory(new MailCategoryCreateRequest(request.Category));
+
+        var hasNameChanged = !string.Equals(request.PreviousName, request.Category.Name, StringComparison.Ordinal);
+        if (!hasNameChanged)
+        {
+            var requestInfo = _graphClient.Me.Outlook.MasterCategories[request.PreviousRemoteId].ToPatchRequestInformation(new OutlookCategory
+            {
+                Color = GetOutlookCategoryColor(request.Category)
+            });
+
+            return [new HttpRequestBundle<RequestInformation>(requestInfo, request)];
+        }
+
+        var bundles = new List<IRequestBundle<RequestInformation>>();
+        var createRequestInfo = _graphClient.Me.Outlook.MasterCategories.ToPostRequestInformation(new OutlookCategory
+        {
+            DisplayName = request.Category.Name,
+            Color = GetOutlookCategoryColor(request.Category)
+        });
+
+        bundles.Add(new HttpRequestBundle<RequestInformation>(createRequestInfo, request));
+
+        foreach (var target in request.AffectedMessages ?? [])
+        {
+            bundles.Add(new HttpRequestBundle<RequestInformation>(
+                CreateMessageCategoryPatchRequest(target.MessageId, target.CategoryNames),
+                request));
+        }
+
+        bundles.Add(new HttpRequestBundle<RequestInformation>(
+            _graphClient.Me.Outlook.MasterCategories[request.PreviousRemoteId].ToDeleteRequestInformation(),
+            request));
+
+        return bundles;
+    }
+
+    public override List<IRequestBundle<RequestInformation>> DeleteCategory(MailCategoryDeleteRequest request)
+    {
+        if (string.IsNullOrWhiteSpace(request.PreviousRemoteId))
+            return [];
+
+        var bundles = new List<IRequestBundle<RequestInformation>>();
+
+        foreach (var target in request.AffectedMessages ?? [])
+        {
+            bundles.Add(new HttpRequestBundle<RequestInformation>(
+                CreateMessageCategoryPatchRequest(target.MessageId, target.CategoryNames),
+                request));
+        }
+
+        bundles.Add(new HttpRequestBundle<RequestInformation>(
+            _graphClient.Me.Outlook.MasterCategories[request.PreviousRemoteId].ToDeleteRequestInformation(),
+            request));
+
+        return bundles;
+    }
+
+    private RequestInformation CreateMessageCategoryPatchRequest(string messageId, IReadOnlyList<string> categoryNames)
+        => _graphClient.Me.Messages[messageId].ToPatchRequestInformation(new Message
+        {
+            Categories = categoryNames?.ToList() ?? []
+        });
+
     public override async Task DownloadMissingMimeMessageAsync(MailCopy mailItem,
                                                            MailKit.ITransferProgress transferProgress = null,
                                                            CancellationToken cancellationToken = default)
@@ -1962,7 +2090,9 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
         for (int i = 0; i < itemCount; i++)
         {
             var bundle = batch.ElementAt(i);
-            requiresSerial |= bundle.UIChangeRequest is SendDraftRequest;
+            requiresSerial |= bundle.UIChangeRequest is SendDraftRequest
+                              or MailCategoryUpdateRequest
+                              or MailCategoryDeleteRequest;
 
             // UI changes are already applied in ExecuteNativeRequestsAsync before batching.
             var batchRequestId = await batchContent.AddBatchRequestStepAsync(bundle.NativeRequest);
@@ -2110,7 +2240,10 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
            || request is ChangeFlagRequest
            || request is MarkReadRequest
            || request is ArchiveRequest
+           || request is MailCategoryAssignmentRequest
            || request is RenameFolderRequest
+           || request is MailCategoryUpdateRequest
+           || request is MailCategoryDeleteRequest
            || request is DeleteFolderRequest
            || request is AcceptEventRequest
            || request is DeclineEventRequest
@@ -2165,6 +2298,26 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
                     return;
 
                 await UploadCalendarEventAttachmentsAsync(createCalendarEventRequest, createdEventId, CancellationToken.None).ConfigureAwait(false);
+                return;
+            }
+
+            if (bundle?.UIChangeRequest is MailCategoryCreateRequest createCategoryRequest)
+            {
+                var createdCategoryId = json?["id"]?.GetValue<string>();
+                if (!string.IsNullOrWhiteSpace(createdCategoryId))
+                {
+                    await _mailCategoryService.UpdateRemoteIdAsync(createCategoryRequest.Category.Id, createdCategoryId).ConfigureAwait(false);
+                }
+                return;
+            }
+
+            if (bundle?.UIChangeRequest is MailCategoryUpdateRequest updateCategoryRequest)
+            {
+                var updatedCategoryId = json?["id"]?.GetValue<string>();
+                if (!string.IsNullOrWhiteSpace(updatedCategoryId))
+                {
+                    await _mailCategoryService.UpdateRemoteIdAsync(updateCategoryRequest.Category.Id, updatedCategoryId).ConfigureAwait(false);
+                }
             }
         }
         catch (Exception ex)
@@ -2367,11 +2520,68 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
         // Outlook messages can only be assigned to 1 folder at a time.
         // Therefore we don't need to create multiple copies of the same message for different folders.
         var contacts = ExtractContactsFromOutlookMessage(message);
-        var package = new NewMailItemPackage(mailCopy, mimeMessage, assignedFolder.RemoteFolderId, contacts);
+        var package = new NewMailItemPackage(mailCopy, mimeMessage, assignedFolder.RemoteFolderId, contacts, message.Categories);
 
         return [package];
     }
 
+    private static MailCategoryColorOption GetMailCategoryColorOption(CategoryColor? color)
+        => color switch
+        {
+            CategoryColor.Preset0 => new("#FEE2E2", "#991B1B"),
+            CategoryColor.Preset1 => new("#FFEDD5", "#9A3412"),
+            CategoryColor.Preset2 => new("#FEF3C7", "#92400E"),
+            CategoryColor.Preset3 => new("#ECFCCB", "#3F6212"),
+            CategoryColor.Preset4 => new("#DCFCE7", "#166534"),
+            CategoryColor.Preset5 => new("#CCFBF1", "#115E59"),
+            CategoryColor.Preset6 => new("#CFFAFE", "#155E75"),
+            CategoryColor.Preset7 => new("#DBEAFE", "#1D4ED8"),
+            CategoryColor.Preset8 => new("#E0E7FF", "#4338CA"),
+            CategoryColor.Preset9 => new("#F3E8FF", "#7E22CE"),
+            CategoryColor.Preset10 => new("#FCE7F3", "#9D174D"),
+            CategoryColor.Preset11 => new("#FECACA", "#7F1D1D"),
+            CategoryColor.Preset12 => new("#FED7AA", "#7C2D12"),
+            CategoryColor.Preset13 => new("#FDE68A", "#78350F"),
+            CategoryColor.Preset14 => new("#D9F99D", "#365314"),
+            CategoryColor.Preset15 => new("#BBF7D0", "#14532D"),
+            CategoryColor.Preset16 => new("#99F6E4", "#134E4A"),
+            CategoryColor.Preset17 => new("#A5F3FC", "#164E63"),
+            CategoryColor.Preset18 => new("#BFDBFE", "#1E3A8A"),
+            CategoryColor.Preset19 => new("#DDD6FE", "#5B21B6"),
+            CategoryColor.Preset20 => new("#E5E7EB", "#374151"),
+            CategoryColor.Preset21 => new("#D1D5DB", "#1F2937"),
+            CategoryColor.Preset22 => new("#F3F4F6", "#111827"),
+            CategoryColor.Preset23 => new("#E2E8F0", "#334155"),
+            CategoryColor.Preset24 => new("#F8FAFC", "#475569"),
+            _ => new("#E5E7EB", "#374151")
+        };
+
+    private static CategoryColor GetOutlookCategoryColor(MailCategory category)
+        => (category.BackgroundColorHex?.ToUpperInvariant(), category.TextColorHex?.ToUpperInvariant()) switch
+        {
+            ("#FEE2E2", "#991B1B") => CategoryColor.Preset0,
+            ("#FFEDD5", "#9A3412") => CategoryColor.Preset1,
+            ("#FEF3C7", "#92400E") => CategoryColor.Preset2,
+            ("#ECFCCB", "#3F6212") => CategoryColor.Preset3,
+            ("#DCFCE7", "#166534") => CategoryColor.Preset4,
+            ("#CCFBF1", "#115E59") => CategoryColor.Preset5,
+            ("#CFFAFE", "#155E75") => CategoryColor.Preset6,
+            ("#DBEAFE", "#1D4ED8") => CategoryColor.Preset7,
+            ("#E0E7FF", "#4338CA") => CategoryColor.Preset8,
+            ("#F3E8FF", "#7E22CE") => CategoryColor.Preset9,
+            ("#FCE7F3", "#9D174D") => CategoryColor.Preset10,
+            ("#FECACA", "#7F1D1D") => CategoryColor.Preset11,
+            ("#FED7AA", "#7C2D12") => CategoryColor.Preset12,
+            ("#FDE68A", "#78350F") => CategoryColor.Preset13,
+            ("#D9F99D", "#365314") => CategoryColor.Preset14,
+            ("#BBF7D0", "#14532D") => CategoryColor.Preset15,
+            ("#99F6E4", "#134E4A") => CategoryColor.Preset16,
+            ("#A5F3FC", "#164E63") => CategoryColor.Preset17,
+            ("#BFDBFE", "#1E3A8A") => CategoryColor.Preset18,
+            ("#DDD6FE", "#5B21B6") => CategoryColor.Preset19,
+            _ => CategoryColor.Preset0
+        };
+
     private async Task TryMapCalendarInvitationAsync(MailCopy mailCopy, MimeMessage mimeMessage, CancellationToken cancellationToken)
     {
         if (mailCopy.ItemType != MailItemType.CalendarInvitation || mimeMessage == null)
@@ -2674,6 +2884,7 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
                 {
                     existingLocalCalendar.Name = calendar.Name;
                     existingLocalCalendar.IsPrimary = string.Equals(existingLocalCalendar.RemoteCalendarId, remotePrimaryCalendarId, StringComparison.OrdinalIgnoreCase);
+                    existingLocalCalendar.IsReadOnly = !calendar.CanEdit.GetValueOrDefault(true);
                     existingLocalCalendar.BackgroundColorHex = resolvedColor;
                     existingLocalCalendar.TextColorHex = ColorHelpers.GetReadableTextColorHex(existingLocalCalendar.BackgroundColorHex);
 
@@ -2712,12 +2923,14 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
         var remoteCalendarName = calendar.Name;
         var remoteBackgroundColor = ResolveSynchronizedCalendarBackgroundColor(GetRemoteOutlookCalendarBackgroundColor(calendar), accountCalendar);
         var remoteIsPrimary = string.Equals(calendar.Id, remotePrimaryCalendarId, StringComparison.OrdinalIgnoreCase);
+        var remoteIsReadOnly = !calendar.CanEdit.GetValueOrDefault(true);
 
         bool isNameChanged = !string.Equals(accountCalendar.Name, remoteCalendarName, StringComparison.OrdinalIgnoreCase);
         bool isBackgroundColorChanged = !string.Equals(accountCalendar.BackgroundColorHex, remoteBackgroundColor, StringComparison.OrdinalIgnoreCase);
         bool isPrimaryChanged = accountCalendar.IsPrimary != remoteIsPrimary;
+        bool isReadOnlyChanged = accountCalendar.IsReadOnly != remoteIsReadOnly;
 
-        return isNameChanged || isBackgroundColorChanged || isPrimaryChanged;
+        return isNameChanged || isBackgroundColorChanged || isPrimaryChanged || isReadOnlyChanged;
     }
 
     private static string GetRemoteOutlookCalendarBackgroundColor(Calendar calendar)

Wino.Core/Synchronizers/WinoSynchronizer.cs

@@ -20,6 +20,7 @@ using Wino.Core.Domain.Models.MailItem;
 using Wino.Core.Domain.Models.Synchronization;
 using Wino.Core.Requests.Bundles;
 using Wino.Core.Requests.Calendar;
+using Wino.Core.Requests.Category;
 using Wino.Core.Requests.Folder;
 using Wino.Core.Requests.Mail;
 using Wino.Messaging.UI;
@@ -63,6 +64,7 @@ public abstract class WinoSynchronizer<TBaseRequest, TMessageType, TCalendarEven
     /// Only available for Gmail right now.
     /// </summary>
     protected virtual Task SynchronizeAliasesAsync() => Task.CompletedTask;
+    protected virtual Task SynchronizeCategoriesAsync(CancellationToken cancellationToken = default) => Task.CompletedTask;
 
     /// <summary>
     /// Queues all mail ids for initial synchronization for a specific folder.
@@ -194,6 +196,9 @@ public abstract class WinoSynchronizer<TBaseRequest, TMessageType, TCalendarEven
                             case MailSynchronizerOperation.Archive:
                                 nativeRequests.AddRange(Archive(new BatchArchiveRequest(group.Cast<ArchiveRequest>())));
                                 break;
+                            case MailSynchronizerOperation.UpdateCategories:
+                                nativeRequests.AddRange(UpdateCategories(new BatchMailCategoryAssignmentRequest(group.Cast<MailCategoryAssignmentRequest>())));
+                                break;
                             default:
                                 break;
                         }
@@ -221,6 +226,23 @@ public abstract class WinoSynchronizer<TBaseRequest, TMessageType, TCalendarEven
                                 break;
                         }
                     }
+                    else if (key is CategorySynchronizerOperation categorySynchronizerOperation)
+                    {
+                        switch (categorySynchronizerOperation)
+                        {
+                            case CategorySynchronizerOperation.CreateCategory:
+                                nativeRequests.AddRange(CreateCategory(group.ElementAt(0) as MailCategoryCreateRequest));
+                                break;
+                            case CategorySynchronizerOperation.UpdateCategory:
+                                nativeRequests.AddRange(UpdateCategory(group.ElementAt(0) as MailCategoryUpdateRequest));
+                                break;
+                            case CategorySynchronizerOperation.DeleteCategory:
+                                nativeRequests.AddRange(DeleteCategory(group.ElementAt(0) as MailCategoryDeleteRequest));
+                                break;
+                            default:
+                                break;
+                        }
+                    }
                 }
 
                 changeRequestQueue.Clear();
@@ -322,6 +344,30 @@ public abstract class WinoSynchronizer<TBaseRequest, TMessageType, TCalendarEven
                 }
             }
 
+            // Category definition sync.
+            if (options.Type == MailSynchronizationType.Categories)
+            {
+                if (!Account.IsCategorySyncSupported) return MailSynchronizationResult.Empty;
+
+                try
+                {
+                    await SynchronizeCategoriesAsync(activeSynchronizationCancellationToken);
+
+                    return FinalizeMailResult(MailSynchronizationResult.Empty);
+                }
+                catch (AuthenticationAttentionException)
+                {
+                    throw;
+                }
+                catch (Exception ex)
+                {
+                    Log.Error(ex, "Failed to update categories for {Name}", Account.Name);
+
+                    CaptureSynchronizationIssue(SynchronizationIssue.FromException(ex, "CategorySync"));
+                    return FinalizeMailResult(MailSynchronizationResult.Failed(ex));
+                }
+            }
+
             if (shouldDelayExecution)
             {
                 await Task.Delay(maxExecutionDelay);
@@ -526,6 +572,16 @@ public abstract class WinoSynchronizer<TBaseRequest, TMessageType, TCalendarEven
     /// <returns>New synchronization options with minimal HTTP effort.</returns>
     private MailSynchronizationOptions GetSynchronizationOptionsAfterRequestExecution(List<IRequestBase> requests, Guid existingSynchronizationId)
     {
+        if (requests.All(a => a is ICategoryActionRequest or MailCategoryAssignmentRequest))
+        {
+            return new MailSynchronizationOptions
+            {
+                AccountId = Account.Id,
+                Id = existingSynchronizationId,
+                Type = MailSynchronizationType.FoldersOnly
+            };
+        }
+
         List<Guid> synchronizationFolderIds = requests
                 .Where(a => a is ICustomFolderSynchronizationRequest)
                 .Cast<ICustomFolderSynchronizationRequest>()
@@ -602,6 +658,10 @@ public abstract class WinoSynchronizer<TBaseRequest, TMessageType, TCalendarEven
     public virtual List<IRequestBundle<TBaseRequest>> MarkFolderAsRead(MarkFolderAsReadRequest request) => throw new NotSupportedException(string.Format(Translator.Exception_UnsupportedSynchronizerOperation, this.GetType()));
     public virtual List<IRequestBundle<TBaseRequest>> DeleteFolder(DeleteFolderRequest request) => throw new NotSupportedException(string.Format(Translator.Exception_UnsupportedSynchronizerOperation, this.GetType()));
     public virtual List<IRequestBundle<TBaseRequest>> CreateSubFolder(CreateSubFolderRequest request) => throw new NotSupportedException(string.Format(Translator.Exception_UnsupportedSynchronizerOperation, this.GetType()));
+    public virtual List<IRequestBundle<TBaseRequest>> UpdateCategories(BatchMailCategoryAssignmentRequest request) => throw new NotSupportedException(string.Format(Translator.Exception_UnsupportedSynchronizerOperation, this.GetType()));
+    public virtual List<IRequestBundle<TBaseRequest>> CreateCategory(MailCategoryCreateRequest request) => throw new NotSupportedException(string.Format(Translator.Exception_UnsupportedSynchronizerOperation, this.GetType()));
+    public virtual List<IRequestBundle<TBaseRequest>> UpdateCategory(MailCategoryUpdateRequest request) => throw new NotSupportedException(string.Format(Translator.Exception_UnsupportedSynchronizerOperation, this.GetType()));
+    public virtual List<IRequestBundle<TBaseRequest>> DeleteCategory(MailCategoryDeleteRequest request) => throw new NotSupportedException(string.Format(Translator.Exception_UnsupportedSynchronizerOperation, this.GetType()));
 
     #endregion
 

Wino.Mail.ViewModels/AccountDetailsPageViewModel.cs

@@ -169,6 +169,10 @@ public partial class AccountDetailsPageViewModel : MailBaseViewModel
     private void EditAliases()
         => Messenger.Send(new BreadcrumbNavigationRequested(Translator.SettingsManageAliases_Title, WinoPage.AliasManagementPage, Account.Id));
 
+    [RelayCommand]
+    private void EditCategories()
+        => Messenger.Send(new BreadcrumbNavigationRequested(Translator.MailCategoryManagementPage_Title, WinoPage.MailCategoryManagementPage, Account.Id));
+
     [RelayCommand]
     private void EditImapCalDavSettings()
         => Messenger.Send(new BreadcrumbNavigationRequested(

Wino.Mail.ViewModels/AccountSetupProgressPageViewModel.cs

@@ -81,6 +81,10 @@ public partial class AccountSetupProgressPageViewModel : MailBaseViewModel
             Steps.Add(new AccountSetupStepModel { Title = Translator.AccountSetup_Step_FetchingProfile });
             Steps.Add(new AccountSetupStepModel { Title = Translator.AccountSetup_Step_SavingAccount });
             Steps.Add(new AccountSetupStepModel { Title = Translator.AccountSetup_Step_SyncingFolders });
+            if (WizardContext.SelectedProvider.Type == MailProviderType.Outlook)
+            {
+                Steps.Add(new AccountSetupStepModel { Title = Translator.AccountSetup_Step_SyncingCategories });
+            }
             Steps.Add(new AccountSetupStepModel { Title = Translator.AccountSetup_Step_FetchingCalendarMetadata });
             Steps.Add(new AccountSetupStepModel { Title = Translator.AccountSetup_Step_SyncingAliases });
             Steps.Add(new AccountSetupStepModel { Title = Translator.AccountSetup_Step_Finalizing });
@@ -229,6 +233,16 @@ public partial class AccountSetupProgressPageViewModel : MailBaseViewModel
                     throw new Exception(Translator.Exception_FailedToSynchronizeFolders);
                 SetCurrentStepSucceeded();
 
+                // Step: Categories
+                if (_createdAccount.IsCategorySyncSupported)
+                {
+                    SetStepInProgress(Translator.AccountSetup_Step_SyncingCategories);
+                    var categoryResult = await SynchronizationManager.Instance.SynchronizeCategoriesAsync(_createdAccount.Id);
+                    if (categoryResult.CompletedState != SynchronizationCompletedState.Success)
+                        throw new Exception(Translator.Exception_FailedToSynchronizeCategories);
+                    SetCurrentStepSucceeded();
+                }
+
                 // Step: Calendar metadata
                 SetStepInProgress(Translator.AccountSetup_Step_FetchingCalendarMetadata);
                 if (_createdAccount.IsCalendarAccessGranted)

Wino.Mail.ViewModels/MailAppShellViewModel.cs

@@ -73,6 +73,7 @@ public partial class MailAppShellViewModel : MailBaseViewModel,
     public IMenuItem CreatePrimaryMenuItem => CreateMailMenuItem;
 
     private readonly IFolderService _folderService;
+    private readonly IMailCategoryService _mailCategoryService;
     private readonly IConfigurationService _configurationService;
     private readonly IStartupBehaviorService _startupBehaviorService;
     private readonly IAccountService _accountService;
@@ -99,6 +100,7 @@ public partial class MailAppShellViewModel : MailBaseViewModel,
                              IMimeFileService mimeFileService,
                              INativeAppService nativeAppService,
                              IMailService mailService,
+                             IMailCategoryService mailCategoryService,
                              IAccountService accountService,
                              IContextMenuItemService contextMenuItemService,
                              IStoreRatingService storeRatingService,
@@ -125,6 +127,7 @@ public partial class MailAppShellViewModel : MailBaseViewModel,
         _mimeFileService = mimeFileService;
         _nativeAppService = nativeAppService;
         _mailService = mailService;
+        _mailCategoryService = mailCategoryService;
         _folderService = folderService;
         _accountService = accountService;
         _contextMenuItemService = contextMenuItemService;
@@ -721,7 +724,8 @@ public partial class MailAppShellViewModel : MailBaseViewModel,
         {
             await HandleCreateNewMailAsync();
         }
-        else if (clickedMenuItem is IBaseFolderMenuItem baseFolderMenuItem && baseFolderMenuItem.HandlingFolders.All(a => a.IsMoveTarget))
+        else if (clickedMenuItem is IBaseFolderMenuItem baseFolderMenuItem &&
+                 (clickedMenuItem is IMailCategoryMenuItem or IMergedMailCategoryMenuItem || baseFolderMenuItem.HandlingFolders.All(a => a.IsMoveTarget)))
         {
             // Don't navigate to base folders that contain non-move target folders.
             // Theory: This is a special folder like Categories or More. Don't navigate to it.
@@ -793,11 +797,20 @@ public partial class MailAppShellViewModel : MailBaseViewModel,
     {
         // Get visible account menu items, ordered by merged accounts at the last.
         // We will update the unread counts for all single accounts and trigger UI refresh for merged menu items.
-        var accountMenuItems = MenuItems.GetAllAccountMenuItems().OrderBy(a => a.HoldingAccounts.Count());
+        List<IAccountMenuItem> accountMenuItems = null;
+
+        await ExecuteUIThread(() =>
+        {
+            accountMenuItems = MenuItems
+                .GetAllAccountMenuItems()
+                .OrderBy(a => a.HoldingAccounts.Count())
+                .ToList();
+        });
 
         // Individually get all single accounts' unread counts.
-        var accountIds = accountMenuItems.OfType<AccountMenuItem>().Select(a => a.AccountId);
+        var accountIds = accountMenuItems.OfType<AccountMenuItem>().Select(a => a.AccountId).ToList();
         var unreadCountResult = await _folderService.GetUnreadItemCountResultsAsync(accountIds).ConfigureAwait(false);
+        var unreadCategoryCountResult = await _mailCategoryService.GetUnreadCategoryCountResultsAsync(accountIds).ConfigureAwait(false);
 
         // Recursively update all folders' unread counts to 0.
         // Query above only returns unread counts that exists. We need to reset the rest to 0 first.
@@ -849,6 +862,29 @@ public partial class MailAppShellViewModel : MailBaseViewModel,
             }
         }
 
+        foreach (var unreadCategoryCount in unreadCategoryCountResult)
+        {
+            if (MenuItems.TryGetCategoryMenuItem(unreadCategoryCount.CategoryId, out var categoryMenuItem))
+            {
+                if (categoryMenuItem is IMergedMailCategoryMenuItem mergedCategoryMenuItem)
+                {
+                    await ExecuteUIThread(() =>
+                    {
+                        categoryMenuItem.UnreadItemCount = unreadCategoryCountResult
+                            .Where(a => mergedCategoryMenuItem.Categories.Any(b => b.Id == a.CategoryId))
+                            .Sum(a => a.UnreadItemCount);
+                    });
+                }
+                else
+                {
+                    await ExecuteUIThread(() =>
+                    {
+                        categoryMenuItem.UnreadItemCount = unreadCategoryCount.UnreadItemCount;
+                    });
+                }
+            }
+        }
+
         // Update unread badge after all unread counts are updated.
         await _notificationBuilder.UpdateTaskbarIconBadgeAsync();
     }

Wino.Mail.ViewModels/MailCategoryManagementPageViewModel.cs

@@ -0,0 +1,251 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Threading.Tasks;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using Wino.Core.Domain;
+using Wino.Core.Domain.Entities.Mail;
+using Wino.Core.Domain.Entities.Shared;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Interfaces;
+using Wino.Core.Domain.Models.MailItem;
+using Wino.Core.Domain.Models.Navigation;
+using Wino.Core.Domain.Models.Synchronization;
+using Wino.Core.Requests.Category;
+using Wino.Core.Services;
+
+namespace Wino.Mail.ViewModels;
+
+public partial class MailCategoryManagementPageViewModel : MailBaseViewModel
+{
+    private readonly IMailCategoryService _mailCategoryService;
+    private readonly IAccountService _accountService;
+    private readonly IMailDialogService _dialogService;
+    private readonly IWinoRequestDelegator _winoRequestDelegator;
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(CanRefresh))]
+    public partial MailAccount Account { get; set; }
+
+    public ObservableCollection<MailCategory> Categories { get; } = [];
+
+    public bool CanRefresh => Account?.ProviderType == MailProviderType.Outlook;
+    public bool HasCategories => Categories.Count > 0;
+
+    public MailCategoryManagementPageViewModel(
+        IMailCategoryService mailCategoryService,
+        IAccountService accountService,
+        IMailDialogService dialogService,
+        IWinoRequestDelegator winoRequestDelegator)
+    {
+        _mailCategoryService = mailCategoryService;
+        _accountService = accountService;
+        _dialogService = dialogService;
+        _winoRequestDelegator = winoRequestDelegator;
+    }
+
+    public override async void OnNavigatedTo(NavigationMode mode, object parameters)
+    {
+        base.OnNavigatedTo(mode, parameters);
+
+        if (parameters is not Guid accountId)
+            return;
+
+        Account = await _accountService.GetAccountAsync(accountId).ConfigureAwait(false);
+
+        if (Account != null)
+        {
+            await LoadCategoriesAsync().ConfigureAwait(false);
+        }
+    }
+
+    [RelayCommand]
+    private Task AddCategoryAsync()
+        => CreateOrUpdateCategoryAsync();
+
+    [RelayCommand]
+    private async Task RefreshCategoriesAsync()
+    {
+        if (!CanRefresh)
+            return;
+
+        var shouldContinue = await _dialogService.ShowConfirmationDialogAsync(
+            Translator.MailCategoryManagementPage_RefreshConfirmationMessage,
+            Translator.Buttons_Refresh,
+            Translator.Buttons_Refresh).ConfigureAwait(false);
+
+        if (!shouldContinue)
+            return;
+
+        await _mailCategoryService.DeleteCategoriesAsync(Account.Id).ConfigureAwait(false);
+        await SynchronizationManager.Instance.SynchronizeCategoriesAsync(Account.Id).ConfigureAwait(false);
+
+        await LoadCategoriesAsync().ConfigureAwait(false);
+    }
+
+    public Task EditCategoryAsync(MailCategory category)
+        => CreateOrUpdateCategoryAsync(category);
+
+    public async Task DeleteCategoryAsync(MailCategory category)
+    {
+        if (category == null)
+            return;
+
+        var shouldDelete = await _dialogService.ShowConfirmationDialogAsync(
+            string.Format(Translator.MailCategoryManagementPage_DeleteConfirmationMessage, category.Name),
+            Translator.MailCategoryManagementPage_DeleteConfirmationTitle,
+            Translator.Buttons_Delete).ConfigureAwait(false);
+
+        if (!shouldDelete)
+            return;
+
+        var deleteRequest = await BuildDeleteCategoryRequestAsync(category).ConfigureAwait(false);
+        await _mailCategoryService.DeleteCategoryAsync(category.Id).ConfigureAwait(false);
+        await QueueOutlookCategoryRequestsAsync(deleteRequest).ConfigureAwait(false);
+        await LoadCategoriesAsync().ConfigureAwait(false);
+    }
+
+    public async Task SetFavoriteAsync(MailCategory category, bool isFavorite)
+    {
+        if (category == null)
+            return;
+
+        await _mailCategoryService.ToggleFavoriteAsync(category.Id, isFavorite).ConfigureAwait(false);
+        await LoadCategoriesAsync().ConfigureAwait(false);
+    }
+
+    private async Task CreateOrUpdateCategoryAsync(MailCategory existingCategory = null)
+    {
+        var dialogResult = await _dialogService.ShowEditMailCategoryDialogAsync(existingCategory).ConfigureAwait(false);
+        if (dialogResult == null)
+            return;
+
+        if (string.IsNullOrWhiteSpace(dialogResult.Name))
+        {
+            await _dialogService.ShowMessageAsync(
+                Translator.MailCategoryDialog_InvalidNameMessage,
+                Translator.MailCategoryDialog_InvalidNameTitle,
+                WinoCustomMessageDialogIcon.Warning).ConfigureAwait(false);
+            return;
+        }
+
+        var normalizedName = dialogResult.Name.Trim();
+        var categoryIdToExclude = existingCategory?.Id;
+        var alreadyExists = await _mailCategoryService.CategoryNameExistsAsync(Account.Id, normalizedName, categoryIdToExclude).ConfigureAwait(false);
+
+        if (alreadyExists)
+        {
+            await _dialogService.ShowMessageAsync(
+                Translator.MailCategoryDialog_DuplicateMessage,
+                Translator.MailCategoryDialog_DuplicateTitle,
+                WinoCustomMessageDialogIcon.Warning).ConfigureAwait(false);
+            return;
+        }
+
+        if (existingCategory == null)
+        {
+            var newCategory = new MailCategory
+            {
+                Id = Guid.NewGuid(),
+                MailAccountId = Account.Id,
+                Name = normalizedName,
+                BackgroundColorHex = dialogResult.BackgroundColorHex,
+                TextColorHex = dialogResult.TextColorHex,
+                Source = Account.ProviderType == MailProviderType.Outlook ? MailCategorySource.Outlook : MailCategorySource.Local
+            };
+
+            await _mailCategoryService.CreateCategoryAsync(newCategory).ConfigureAwait(false);
+
+            if (Account.ProviderType == MailProviderType.Outlook)
+            {
+                await _winoRequestDelegator.ExecuteAsync(Account.Id, [new MailCategoryCreateRequest(newCategory)]).ConfigureAwait(false);
+            }
+        }
+        else
+        {
+            var previousName = existingCategory.Name;
+            var previousRemoteId = existingCategory.RemoteId;
+
+            existingCategory.Name = normalizedName;
+            existingCategory.BackgroundColorHex = dialogResult.BackgroundColorHex;
+            existingCategory.TextColorHex = dialogResult.TextColorHex;
+
+            await _mailCategoryService.UpdateCategoryAsync(existingCategory).ConfigureAwait(false);
+
+            if (Account.ProviderType == MailProviderType.Outlook)
+            {
+                if (string.IsNullOrWhiteSpace(previousRemoteId))
+                {
+                    await _winoRequestDelegator.ExecuteAsync(Account.Id, [new MailCategoryCreateRequest(existingCategory)]).ConfigureAwait(false);
+                }
+                else
+                {
+                    var affectedMessages = await BuildAffectedMessageTargetsAsync(existingCategory.Id).ConfigureAwait(false);
+                    var updateRequest = new MailCategoryUpdateRequest(existingCategory, previousName, previousRemoteId, affectedMessages);
+                    await _winoRequestDelegator.ExecuteAsync(Account.Id, [updateRequest]).ConfigureAwait(false);
+                }
+            }
+        }
+
+        await LoadCategoriesAsync().ConfigureAwait(false);
+    }
+
+    private async Task<MailCategoryDeleteRequest> BuildDeleteCategoryRequestAsync(MailCategory category)
+    {
+        if (category == null || Account?.ProviderType != MailProviderType.Outlook)
+            return null;
+
+        var mailCopies = await _mailCategoryService.GetMailCopiesForCategoryAsync(category.Id).ConfigureAwait(false);
+        var affectedMessages = new List<MailCategoryMessageUpdateTarget>();
+
+        foreach (var mailCopy in mailCopies.Where(a => !string.IsNullOrWhiteSpace(a.Id)))
+        {
+            var remainingNames = await _mailCategoryService.GetCategoryNamesForMailAsync(mailCopy.UniqueId).ConfigureAwait(false);
+            var categoryNames = remainingNames
+                .Where(a => !string.Equals(a, category.Name, StringComparison.OrdinalIgnoreCase))
+                .ToList();
+
+            affectedMessages.Add(new MailCategoryMessageUpdateTarget(mailCopy.Id, categoryNames));
+        }
+
+        return new MailCategoryDeleteRequest(category, category.RemoteId, affectedMessages);
+    }
+
+    private async Task<IReadOnlyList<MailCategoryMessageUpdateTarget>> BuildAffectedMessageTargetsAsync(Guid categoryId)
+    {
+        var mailCopies = await _mailCategoryService.GetMailCopiesForCategoryAsync(categoryId).ConfigureAwait(false);
+        var affectedMessages = new List<MailCategoryMessageUpdateTarget>();
+
+        foreach (var mailCopy in mailCopies.Where(a => !string.IsNullOrWhiteSpace(a.Id)))
+        {
+            var categoryNames = await _mailCategoryService.GetCategoryNamesForMailAsync(mailCopy.UniqueId).ConfigureAwait(false);
+            affectedMessages.Add(new MailCategoryMessageUpdateTarget(mailCopy.Id, categoryNames));
+        }
+
+        return affectedMessages;
+    }
+
+    private Task QueueOutlookCategoryRequestsAsync(params IRequestBase[] requests)
+        => Account?.ProviderType == MailProviderType.Outlook && requests.Any(a => a != null)
+            ? _winoRequestDelegator.ExecuteAsync(Account.Id, requests.Where(a => a != null))
+            : Task.CompletedTask;
+
+    private async Task LoadCategoriesAsync()
+    {
+        var categories = await _mailCategoryService.GetCategoriesAsync(Account.Id).ConfigureAwait(false);
+
+        await ExecuteUIThread(() =>
+        {
+            Categories.Clear();
+
+            foreach (var category in categories)
+            {
+                Categories.Add(category);
+            }
+
+            OnPropertyChanged(nameof(HasCategories));
+        });
+    }
+}

Wino.Mail.ViewModels/MailListPageViewModel.cs

@@ -23,7 +23,7 @@ using Wino.Core.Domain.Models.MailItem;
 using Wino.Core.Domain.Models.Menus;
 using Wino.Core.Domain.Models.Navigation;
 using Wino.Core.Domain.Models.Reader;
-using Wino.Core.Domain.Models.Synchronization;
+using Wino.Core.Requests.Mail;
 using Wino.Core.Services;
 using Wino.Mail.ViewModels.Collections;
 using Wino.Mail.ViewModels.Data;
@@ -77,6 +77,7 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     private readonly INotificationBuilder _notificationBuilder;
     private readonly IFolderService _folderService;
     private readonly IContextMenuItemService _contextMenuItemService;
+    private readonly IMailCategoryService _mailCategoryService;
     private readonly IWinoRequestDelegator _winoRequestDelegator;
     private readonly IKeyPressService _keyPressService;
     private readonly IWinoLogger _winoLogger;
@@ -156,6 +157,8 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(CanSynchronize))]
     [NotifyPropertyChangedFor(nameof(IsFolderSynchronizationEnabled))]
+    [NotifyPropertyChangedFor(nameof(IsCategoryView))]
+    [NotifyPropertyChangedFor(nameof(IsSyncButtonVisible))]
     public partial IBaseFolderMenuItem ActiveFolder { get; set; }
 
     [ObservableProperty]
@@ -172,6 +175,7 @@ public partial class MailListPageViewModel : MailBaseViewModel,
                                  INotificationBuilder notificationBuilder,
                                  IFolderService folderService,
                                  IContextMenuItemService contextMenuItemService,
+                                 IMailCategoryService mailCategoryService,
                                  IWinoRequestDelegator winoRequestDelegator,
                                  IKeyPressService keyPressService,
                                  IPreferencesService preferencesService,
@@ -185,6 +189,7 @@ public partial class MailListPageViewModel : MailBaseViewModel,
         _mimeFileService = mimeFileService;
         _folderService = folderService;
         _contextMenuItemService = contextMenuItemService;
+        _mailCategoryService = mailCategoryService;
         _winoRequestDelegator = winoRequestDelegator;
         _keyPressService = keyPressService;
 
@@ -277,9 +282,11 @@ public partial class MailListPageViewModel : MailBaseViewModel,
         }
     }
 
-    public bool CanSynchronize => !IsAccountSynchronizerInSynchronization && IsFolderSynchronizationEnabled;
+    public bool CanSynchronize => !IsCategoryView && !IsAccountSynchronizerInSynchronization && IsFolderSynchronizationEnabled;
     public bool IsFolderSynchronizationEnabled => ActiveFolder?.IsSynchronizationEnabled ?? false;
     public bool IsArchiveSpecialFolder => ActiveFolder?.SpecialFolderType == SpecialFolderType.Archive;
+    public bool IsCategoryView => ActiveFolder is IMailCategoryMenuItem or IMergedMailCategoryMenuItem;
+    public bool IsSyncButtonVisible => !IsCategoryView;
 
     public string SelectedMessageText => IsDragInProgress
         ? string.Format(Translator.MailsDragging, DraggingItemsCount)
@@ -396,9 +403,12 @@ public partial class MailListPageViewModel : MailBaseViewModel,
         }
         else
         {
+            if (IsCategoryView)
+            {
+                PivotFolders.Add(new FolderPivotViewModel(ActiveFolder.FolderName, null));
+            }
             // Merged folders don't support focused feature.
-
+            else if (ActiveFolder is IMergedAccountFolderMenuItem)
-            if (ActiveFolder is IMergedAccountFolderMenuItem)
             {
                 PivotFolders.Add(new FolderPivotViewModel(ActiveFolder.FolderName, null));
             }
@@ -475,26 +485,29 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     {
         if (!CanSynchronize) return;
 
+        _notificationBuilder.CreateNotificationsAsync(MailCollection.SelectedItems.Select(a => a.MailCopy));
+        return;
+
         // Only synchronize listed folders.
 
         // When doing linked inbox sync, we need to save the sync id to report progress back only once.
         // Otherwise, we will report progress for each folder and that's what we don't want.
 
-        trackingSynchronizationId = Guid.NewGuid();
+        //trackingSynchronizationId = Guid.NewGuid();
-        completedTrackingSynchronizationCount = 0;
+        //completedTrackingSynchronizationCount = 0;
 
-        foreach (var folder in ActiveFolder.HandlingFolders)
+        //foreach (var folder in ActiveFolder.HandlingFolders)
-        {
+        //{
-            var options = new MailSynchronizationOptions()
+        //    var options = new MailSynchronizationOptions()
-            {
+        //    {
-                AccountId = folder.MailAccountId,
+        //        AccountId = folder.MailAccountId,
-                Type = MailSynchronizationType.CustomFolders,
+        //        Type = MailSynchronizationType.CustomFolders,
-                SynchronizationFolderIds = [folder.Id],
+        //        SynchronizationFolderIds = [folder.Id],
-                GroupedSynchronizationTrackingId = trackingSynchronizationId
+        //        GroupedSynchronizationTrackingId = trackingSynchronizationId
-            };
+        //    };
 
-            Messenger.Send(new NewMailSynchronizationRequested(options));
+        //    Messenger.Send(new NewMailSynchronizationRequested(options));
-        }
+        //}
     }
 
     [RelayCommand]
@@ -545,7 +558,7 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     [RelayCommand]
     private async Task EnableFolderSynchronizationAsync()
     {
-        if (ActiveFolder == null) return;
+        if (ActiveFolder == null || IsCategoryView) return;
 
         foreach (var folder in ActiveFolder.HandlingFolders)
         {
@@ -561,13 +574,9 @@ public partial class MailListPageViewModel : MailBaseViewModel,
         Debug.WriteLine("Loading more...");
         await ExecuteUIThread(() => { IsInitializingFolder = true; });
 
-        var initializationOptions = new MailListInitializationOptions(ActiveFolder.HandlingFolders,
+        var initializationOptions = CreateInitializationOptions(
-                                                                      SelectedFilterOption.Type,
+            IsInSearchMode ? SearchQuery : string.Empty,
-                                                                      SelectedSortingOption.Type,
+            MailCollection.MailCopyIdHashSet);
-                                                                      PreferencesService.IsThreadingEnabled,
-                                                                      SelectedFolderPivot.IsFocused,
-                                                                      IsInSearchMode ? SearchQuery : string.Empty,
-                                                                      MailCollection.MailCopyIdHashSet);
 
         var items = await _mailService.FetchMailsAsync(initializationOptions).ConfigureAwait(false);
 
@@ -674,6 +683,60 @@ public partial class MailListPageViewModel : MailBaseViewModel,
     public IEnumerable<MailOperationMenuItem> GetAvailableMailActions(IEnumerable<MailItemViewModel> contextMailItems)
         => _contextMenuItemService.GetMailItemContextMenuActions(contextMailItems.Select(a => a.MailCopy));
 
+    public async Task<(IReadOnlyList<MailCategory> Categories, IReadOnlyCollection<Guid> AssignedCategoryIds)> GetAvailableCategoriesAsync(IEnumerable<MailItemViewModel> targetItems)
+    {
+        var targetList = targetItems?.Where(a => a?.MailCopy?.AssignedAccount != null).ToList() ?? [];
+        if (targetList.Count == 0)
+            return ([], []);
+
+        var accountIds = targetList.Select(a => a.MailCopy.AssignedAccount.Id).Distinct().ToList();
+        if (accountIds.Count != 1)
+            return ([], []);
+
+        var accountId = accountIds[0];
+        var uniqueIds = targetList.Select(a => a.MailCopy.UniqueId).Distinct().ToList();
+
+        var categories = await _mailCategoryService.GetCategoriesAsync(accountId).ConfigureAwait(false);
+        var assignedCategoryIds = await _mailCategoryService.GetAssignedCategoryIdsForAllAsync(uniqueIds).ConfigureAwait(false);
+
+        return (categories, assignedCategoryIds);
+    }
+
+    public async Task ToggleCategoryAssignmentAsync(MailCategory category, IEnumerable<MailItemViewModel> targetItems, bool isAssignedToAll)
+    {
+        var targetList = targetItems?.Where(a => a?.MailCopy?.AssignedAccount != null).ToList() ?? [];
+        if (category == null || targetList.Count == 0)
+            return;
+
+        var accountIds = targetList.Select(a => a.MailCopy.AssignedAccount.Id).Distinct().ToList();
+        if (accountIds.Count != 1)
+            return;
+
+        var accountId = accountIds[0];
+        var uniqueIds = targetList.Select(a => a.MailCopy.UniqueId).Distinct().ToList();
+
+        if (isAssignedToAll)
+        {
+            await _mailCategoryService.UnassignCategoryAsync(category.Id, uniqueIds).ConfigureAwait(false);
+        }
+        else
+        {
+            await _mailCategoryService.AssignCategoryAsync(category.Id, uniqueIds).ConfigureAwait(false);
+        }
+
+        if (targetList.First().MailCopy.AssignedAccount.ProviderType != MailProviderType.Outlook)
+            return;
+
+        var requests = new List<IRequestBase>();
+        foreach (var mailItem in targetList.Select(a => a.MailCopy).DistinctBy(a => a.UniqueId))
+        {
+            var categoryNames = await _mailCategoryService.GetCategoryNamesForMailAsync(mailItem.UniqueId).ConfigureAwait(false);
+            requests.Add(new MailCategoryAssignmentRequest(mailItem, category.Id, category.Name, categoryNames, !isAssignedToAll));
+        }
+
+        await _winoRequestDelegator.ExecuteAsync(accountId, requests).ConfigureAwait(false);
+    }
+
     private bool ShouldPreventItemAdd(MailCopy mailItem)
     {
         bool condition = mailItem.IsRead
@@ -691,7 +754,7 @@ public partial class MailListPageViewModel : MailBaseViewModel,
         => ActiveFolder?.SpecialFolderType == SpecialFolderType.Draft;
 
     private bool BelongsToActiveFolder(MailCopy mailItem)
-        => mailItem?.AssignedFolder != null && ActiveFolder?.HandlingFolders?.Any(a => a.Id == mailItem.AssignedFolder.Id) == true;
+        => !IsCategoryView && mailItem?.AssignedFolder != null && ActiveFolder?.HandlingFolders?.Any(a => a.Id == mailItem.AssignedFolder.Id) == true;
 
     private bool ShouldIncludeByThread(MailCopy mailItem)
         => PreferencesService.IsThreadingEnabled
@@ -1069,6 +1132,38 @@ public partial class MailListPageViewModel : MailBaseViewModel,
         }
     }
 
+    private MailListInitializationOptions CreateInitializationOptions(
+        string searchQuery,
+        System.Collections.Concurrent.ConcurrentDictionary<Guid, bool> existingUniqueIds,
+        List<MailCopy> preFetchedMailCopies = null,
+        bool deduplicateByServerId = false)
+    {
+        var options = new MailListInitializationOptions(ActiveFolder.HandlingFolders,
+                                                        SelectedFilterOption.Type,
+                                                        SelectedSortingOption.Type,
+                                                        PreferencesService.IsThreadingEnabled,
+                                                        SelectedFolderPivot.IsFocused,
+                                                        searchQuery,
+                                                        existingUniqueIds,
+                                                        preFetchedMailCopies,
+                                                        DeduplicateByServerId: deduplicateByServerId);
+
+        if (!IsCategoryView)
+            return options;
+
+        var categoryIds = ActiveFolder switch
+        {
+            IMailCategoryMenuItem singleCategoryMenuItem => new List<Guid> { singleCategoryMenuItem.MailCategory.Id },
+            IMergedMailCategoryMenuItem mergedCategoryMenuItem => mergedCategoryMenuItem.Categories.Select(a => a.Id).ToList(),
+            _ => []
+        };
+
+        return options with
+        {
+            CategoryIds = categoryIds
+        };
+    }
+
     [RelayCommand]
     private async Task PerformOnlineSearchAsync()
     {
@@ -1218,15 +1313,11 @@ public partial class MailListPageViewModel : MailBaseViewModel,
                 }
             }
 
-            var initializationOptions = new MailListInitializationOptions(ActiveFolder.HandlingFolders,
+            var initializationOptions = CreateInitializationOptions(
-                                                                          SelectedFilterOption.Type,
+                isDoingOnlineSearch ? string.Empty : SearchQuery,
-                                                                          SelectedSortingOption.Type,
+                MailCollection.MailCopyIdHashSet,
-                                                                          PreferencesService.IsThreadingEnabled,
+                onlineSearchItems,
-                                                                          SelectedFolderPivot.IsFocused,
+                isDoingOnlineSearch);
-                                                                          isDoingOnlineSearch ? string.Empty : SearchQuery,
-                                                                          MailCollection.MailCopyIdHashSet,
-                                                                          onlineSearchItems,
-                                                                          DeduplicateByServerId: isDoingOnlineSearch);
 
             items = await _mailService.FetchMailsAsync(initializationOptions, cancellationToken).ConfigureAwait(false);
 

Wino.Mail.ViewModels/MailNotificationSettingsPageViewModel.cs

@@ -0,0 +1,135 @@
+using System.Collections.ObjectModel;
+using System.Linq;
+using CommunityToolkit.Mvvm.ComponentModel;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Interfaces;
+using Wino.Core.Domain;
+
+namespace Wino.Mail.ViewModels;
+
+public partial class MailNotificationSettingsPageViewModel : MailBaseViewModel
+{
+    private static readonly MailOperation[] SupportedMailNotificationActions =
+    [
+        MailOperation.MarkAsRead,
+        MailOperation.SoftDelete,
+        MailOperation.MoveToJunk,
+        MailOperation.Archive,
+        MailOperation.Reply,
+        MailOperation.ReplyAll,
+        MailOperation.Forward
+    ];
+
+    private readonly IPreferencesService _preferencesService;
+    private bool _isUpdatingSelection;
+    private bool _isLoaded;
+
+    public ObservableCollection<MailNotificationActionOption> AvailableNotificationActions { get; } = [];
+
+    [ObservableProperty]
+    public partial MailNotificationActionOption SelectedFirstAction { get; set; }
+
+    [ObservableProperty]
+    public partial MailNotificationActionOption SelectedSecondAction { get; set; }
+
+    public MailNotificationSettingsPageViewModel(IPreferencesService preferencesService)
+    {
+        _preferencesService = preferencesService;
+
+        foreach (var action in SupportedMailNotificationActions)
+        {
+            AvailableNotificationActions.Add(new MailNotificationActionOption(action, GetOperationDisplayText(action)));
+        }
+
+        InitializeSelections();
+        _isLoaded = true;
+    }
+
+    partial void OnSelectedFirstActionChanged(MailNotificationActionOption value)
+    {
+        if (!_isLoaded || _isUpdatingSelection || value == null)
+            return;
+
+        EnsureDistinctSelections(changedSelection: value, isFirstSelection: true);
+        _preferencesService.FirstMailNotificationAction = value.Operation;
+    }
+
+    partial void OnSelectedSecondActionChanged(MailNotificationActionOption value)
+    {
+        if (!_isLoaded || _isUpdatingSelection || value == null)
+            return;
+
+        EnsureDistinctSelections(changedSelection: value, isFirstSelection: false);
+        _preferencesService.SecondMailNotificationAction = value.Operation;
+    }
+
+    private void InitializeSelections()
+    {
+        var firstAction = ResolveSupportedAction(_preferencesService.FirstMailNotificationAction, MailOperation.MarkAsRead);
+        var secondAction = ResolveSupportedAction(_preferencesService.SecondMailNotificationAction, MailOperation.SoftDelete);
+
+        if (secondAction == firstAction)
+        {
+            secondAction = GetFallbackDistinctAction(firstAction);
+        }
+
+        SelectedFirstAction = GetOption(firstAction);
+        SelectedSecondAction = GetOption(secondAction);
+
+        _preferencesService.FirstMailNotificationAction = firstAction;
+        _preferencesService.SecondMailNotificationAction = secondAction;
+    }
+
+    private void EnsureDistinctSelections(MailNotificationActionOption changedSelection, bool isFirstSelection)
+    {
+        var otherSelection = isFirstSelection ? SelectedSecondAction : SelectedFirstAction;
+        if (otherSelection?.Operation != changedSelection.Operation)
+            return;
+
+        _isUpdatingSelection = true;
+
+        var fallbackAction = GetFallbackDistinctAction(changedSelection.Operation);
+        var fallbackOption = GetOption(fallbackAction);
+
+        if (isFirstSelection)
+        {
+            SelectedSecondAction = fallbackOption;
+            _preferencesService.SecondMailNotificationAction = fallbackAction;
+        }
+        else
+        {
+            SelectedFirstAction = fallbackOption;
+            _preferencesService.FirstMailNotificationAction = fallbackAction;
+        }
+
+        _isUpdatingSelection = false;
+    }
+
+    private MailNotificationActionOption GetOption(MailOperation action)
+        => AvailableNotificationActions.First(option => option.Operation == action);
+
+    private static MailOperation ResolveSupportedAction(MailOperation action, MailOperation fallbackAction)
+        => SupportedMailNotificationActions.Contains(action) ? action : fallbackAction;
+
+    private static MailOperation GetFallbackDistinctAction(MailOperation excludedAction)
+        => SupportedMailNotificationActions.First(action => action != excludedAction);
+
+    private static string GetOperationDisplayText(MailOperation action)
+        => action switch
+        {
+            MailOperation.MarkAsRead => Translator.MailOperation_MarkAsRead,
+            MailOperation.SoftDelete => Translator.MailOperation_Delete,
+            MailOperation.MoveToJunk => Translator.MailOperation_MarkAsJunk,
+            MailOperation.Archive => Translator.MailOperation_Archive,
+            MailOperation.Reply => Translator.MailOperation_Reply,
+            MailOperation.ReplyAll => Translator.MailOperation_ReplyAll,
+            MailOperation.Forward => Translator.MailOperation_Forward,
+            _ => action.ToString()
+        };
+}
+
+public sealed class MailNotificationActionOption(MailOperation operation, string displayText)
+{
+    public MailOperation Operation { get; } = operation;
+    public string DisplayText { get; } = displayText;
+}

Wino.Mail.WinUI/Activation/AppNotificationActivationBuffer.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Windows.AppNotifications;
+
+namespace Wino.Mail.WinUI.Activation;
+
+internal sealed record BufferedAppNotificationActivation(string Argument, IReadOnlyDictionary<string, string>? UserInput);
+
+internal sealed class AppNotificationActivationBuffer
+{
+    private readonly ConcurrentQueue<BufferedAppNotificationActivation> _pendingActivations = new();
+    private readonly SemaphoreSlim _pendingSignal = new(0);
+
+    public void Enqueue(AppNotificationActivatedEventArgs args)
+    {
+        var copiedUserInput = args.UserInput == null
+            ? null
+            : new Dictionary<string, string>(args.UserInput, StringComparer.Ordinal);
+
+        _pendingActivations.Enqueue(new BufferedAppNotificationActivation(args.Argument, copiedUserInput));
+        _pendingSignal.Release();
+    }
+
+    public bool TryDequeue(out BufferedAppNotificationActivation activation)
+        => _pendingActivations.TryDequeue(out activation!);
+
+    public async Task<BufferedAppNotificationActivation?> WaitAsync(TimeSpan timeout, CancellationToken cancellationToken = default)
+    {
+        if (!_pendingActivations.IsEmpty && TryDequeue(out var queuedActivation))
+            return queuedActivation;
+
+        if (!await _pendingSignal.WaitAsync(timeout, cancellationToken))
+            return null;
+
+        return TryDequeue(out var activation) ? activation : null;
+    }
+}

Wino.Mail.WinUI/Activation/CalendarEntryBootstrapActivation.cs

@@ -0,0 +1,207 @@
+using System;
+using System.IO;
+using System.Linq;
+using Microsoft.Windows.AppLifecycle;
+using Windows.ApplicationModel;
+using Windows.ApplicationModel.Activation;
+using Windows.Storage;
+using Wino.Core.Domain.Enums;
+
+namespace Wino.Mail.WinUI.Activation;
+
+internal enum PendingBootstrapActivationKind
+{
+    Launch,
+    Protocol,
+    File
+}
+
+internal sealed class PendingBootstrapActivation
+{
+    public PendingBootstrapActivationKind Kind { get; init; }
+    public WinoApplicationMode Mode { get; init; } = WinoApplicationMode.Mail;
+    public string? LaunchArguments { get; init; }
+    public string? TileId { get; init; }
+    public string? ProtocolUri { get; init; }
+    public string[] FilePaths { get; init; } = [];
+    public DateTimeOffset CreatedAtUtc { get; init; } = DateTimeOffset.UtcNow;
+}
+
+internal static class CalendarEntryBootstrapActivation
+{
+    private const string PendingActivationKey = "PendingCalendarEntryBootstrapActivation";
+    private const string KindKey = "Kind";
+    private const string ModeKey = "Mode";
+    private const string LaunchArgumentsKey = "LaunchArguments";
+    private const string TileIdKey = "TileId";
+    private const string ProtocolUriKey = "ProtocolUri";
+    private const string FilePathsKey = "FilePaths";
+    private const string CreatedAtUtcKey = "CreatedAtUtc";
+    private static readonly TimeSpan PendingActivationLifetime = TimeSpan.FromMinutes(1);
+
+    public static bool ShouldBootstrapToMailHost(AppActivationArguments activationArgs)
+        => TryCreatePendingActivation(activationArgs, out _);
+
+    public static bool QueuePendingActivation(AppActivationArguments activationArgs)
+    {
+        if (!TryCreatePendingActivation(activationArgs, out var pendingActivation))
+            return false;
+
+        ApplicationData.Current.LocalSettings.Values[PendingActivationKey] = CreateCompositeValue(pendingActivation!);
+        return true;
+    }
+
+    public static void ClearPendingActivation()
+        => ApplicationData.Current.LocalSettings.Values.Remove(PendingActivationKey);
+
+    public static PendingBootstrapActivation? ConsumePendingActivation()
+    {
+        if (!ApplicationData.Current.LocalSettings.Values.TryGetValue(PendingActivationKey, out var pendingActivationValue) ||
+            pendingActivationValue is not ApplicationDataCompositeValue compositeValue)
+        {
+            return null;
+        }
+
+        ClearPendingActivation();
+
+        try
+        {
+            var pendingActivation = ParseCompositeValue(compositeValue);
+            if (pendingActivation == null)
+                return null;
+
+            if (DateTimeOffset.UtcNow - pendingActivation.CreatedAtUtc > PendingActivationLifetime)
+                return null;
+
+            return pendingActivation;
+        }
+        catch
+        {
+            return null;
+        }
+    }
+
+    private static ApplicationDataCompositeValue CreateCompositeValue(PendingBootstrapActivation pendingActivation)
+    {
+        var compositeValue = new ApplicationDataCompositeValue
+        {
+            [KindKey] = pendingActivation.Kind.ToString(),
+            [ModeKey] = pendingActivation.Mode.ToString(),
+            [LaunchArgumentsKey] = pendingActivation.LaunchArguments ?? string.Empty,
+            [TileIdKey] = pendingActivation.TileId ?? string.Empty,
+            [ProtocolUriKey] = pendingActivation.ProtocolUri ?? string.Empty,
+            [FilePathsKey] = string.Join("\n", pendingActivation.FilePaths),
+            [CreatedAtUtcKey] = pendingActivation.CreatedAtUtc.ToString("o")
+        };
+
+        return compositeValue;
+    }
+
+    private static PendingBootstrapActivation? ParseCompositeValue(ApplicationDataCompositeValue compositeValue)
+    {
+        if (!Enum.TryParse(compositeValue[KindKey]?.ToString(), ignoreCase: true, out PendingBootstrapActivationKind kind) ||
+            !Enum.TryParse(compositeValue[ModeKey]?.ToString(), ignoreCase: true, out WinoApplicationMode mode) ||
+            !DateTimeOffset.TryParse(compositeValue[CreatedAtUtcKey]?.ToString(), out var createdAtUtc))
+        {
+            return null;
+        }
+
+        return new PendingBootstrapActivation
+        {
+            Kind = kind,
+            Mode = mode,
+            LaunchArguments = GetOptionalCompositeString(compositeValue, LaunchArgumentsKey),
+            TileId = GetOptionalCompositeString(compositeValue, TileIdKey),
+            ProtocolUri = GetOptionalCompositeString(compositeValue, ProtocolUriKey),
+            FilePaths = GetOptionalCompositeString(compositeValue, FilePathsKey)?
+                .Split(['\n'], StringSplitOptions.RemoveEmptyEntries)
+                .Distinct(StringComparer.OrdinalIgnoreCase)
+                .ToArray() ?? [],
+            CreatedAtUtc = createdAtUtc
+        };
+    }
+
+    private static string? GetOptionalCompositeString(ApplicationDataCompositeValue compositeValue, string key)
+    {
+        if (!compositeValue.TryGetValue(key, out var value))
+            return null;
+
+        var stringValue = value?.ToString();
+        return string.IsNullOrWhiteSpace(stringValue) ? null : stringValue;
+    }
+
+    public static bool LaunchMailHost()
+    {
+        var mailAppUserModelId = AppEntryConstants.GetAppUserModelId(WinoApplicationMode.Mail);
+        var appEntries = Package.Current.GetAppListEntriesAsync().AsTask().GetAwaiter().GetResult();
+        var mailEntry = appEntries.FirstOrDefault(entry =>
+            string.Equals(entry.AppUserModelId, mailAppUserModelId, StringComparison.OrdinalIgnoreCase));
+
+        return mailEntry != null && mailEntry.LaunchAsync().AsTask().GetAwaiter().GetResult();
+    }
+
+    private static bool TryCreatePendingActivation(AppActivationArguments activationArgs, out PendingBootstrapActivation? pendingActivation)
+    {
+        pendingActivation = null;
+
+        if (activationArgs.Kind == ExtendedActivationKind.Launch &&
+            activationArgs.Data is ILaunchActivatedEventArgs launchArgs)
+        {
+            var resolvedMode = AppModeActivationResolver.Resolve(launchArgs.Arguments, launchArgs.TileId, Environment.CommandLine);
+            if (resolvedMode != WinoApplicationMode.Calendar)
+                return false;
+
+            pendingActivation = new PendingBootstrapActivation
+            {
+                Kind = PendingBootstrapActivationKind.Launch,
+                Mode = resolvedMode,
+                LaunchArguments = launchArgs.Arguments,
+                TileId = launchArgs.TileId
+            };
+
+            return true;
+        }
+
+        if (activationArgs.Kind == ExtendedActivationKind.Protocol &&
+            activationArgs.Data is IProtocolActivatedEventArgs protocolArgs &&
+            protocolArgs.Uri != null &&
+            (string.Equals(protocolArgs.Uri.Scheme, "webcal", StringComparison.OrdinalIgnoreCase) ||
+             string.Equals(protocolArgs.Uri.Scheme, "webcals", StringComparison.OrdinalIgnoreCase)))
+        {
+            pendingActivation = new PendingBootstrapActivation
+            {
+                Kind = PendingBootstrapActivationKind.Protocol,
+                Mode = WinoApplicationMode.Calendar,
+                ProtocolUri = protocolArgs.Uri.AbsoluteUri
+            };
+
+            return true;
+        }
+
+        if (activationArgs.Kind == ExtendedActivationKind.File &&
+            activationArgs.Data is IFileActivatedEventArgs fileArgs)
+        {
+            var filePaths = fileArgs.Files?
+                .OfType<IStorageItem>()
+                .Where(item => string.Equals(Path.GetExtension(item.Path), ".ics", StringComparison.OrdinalIgnoreCase))
+                .Select(item => item.Path)
+                .Where(path => !string.IsNullOrWhiteSpace(path))
+                .Distinct(StringComparer.OrdinalIgnoreCase)
+                .ToArray();
+
+            if (filePaths == null || filePaths.Length == 0)
+                return false;
+
+            pendingActivation = new PendingBootstrapActivation
+            {
+                Kind = PendingBootstrapActivationKind.File,
+                Mode = WinoApplicationMode.Calendar,
+                FilePaths = filePaths
+            };
+
+            return true;
+        }
+
+        return false;
+    }
+}

Wino.Mail.WinUI/Activation/ToastActivationResolver.cs

@@ -1,4 +1,4 @@
-using System;
+using Microsoft.Windows.AppNotifications;
 using Wino.Core.Domain;
 using Wino.Core.Domain.Enums;
 
@@ -41,39 +41,22 @@ internal static class ToastActivationResolver
             return calendarAction == Constants.ToastCalendarNavigateAction;
         }
 
+        if (toastArguments.TryGetValue(Constants.ToastDismissActionKey, out string _))
+        {
+            return false;
+        }
+
         if (toastArguments.TryGetValue(Constants.ToastActionKey, out MailOperation mailAction))
         {
-            return mailAction == MailOperation.Navigate;
+            return mailAction is MailOperation.Navigate or MailOperation.Reply or MailOperation.ReplyAll or MailOperation.Forward;
         }
 
         return true;
     }
 
-    public static bool TryResolveMode(NotificationArguments toastArguments, out WinoApplicationMode mode)
-    {
-        mode = WinoApplicationMode.Mail;
-
-        if (!toastArguments.TryGetValue(Constants.ToastModeKey, out string toastMode))
-            return false;
-
-        if (string.Equals(toastMode, Constants.ToastModeCalendar, StringComparison.OrdinalIgnoreCase))
-        {
-            mode = WinoApplicationMode.Calendar;
-            return true;
-        }
-
-        if (string.Equals(toastMode, Constants.ToastModeMail, StringComparison.OrdinalIgnoreCase))
-        {
-            mode = WinoApplicationMode.Mail;
-            return true;
-        }
-
-        return false;
-    }
-
     private static bool ContainsKnownToastKey(NotificationArguments toastArguments)
         => toastArguments.TryGetValue(Constants.ToastStoreUpdateActionKey, out string _) ||
-           toastArguments.TryGetValue(Constants.ToastModeKey, out string _) ||
            toastArguments.TryGetValue(Constants.ToastCalendarActionKey, out string _) ||
+           toastArguments.TryGetValue(Constants.ToastDismissActionKey, out string _) ||
            toastArguments.TryGetValue(Constants.ToastActionKey, out string _);
 }