Improving thread mapping for all synchronizers.

Wino.Core/Synchronizers/GmailSynchronizer.cs

@@ -1183,6 +1183,9 @@ public class GmailSynchronizer : WinoSynchronizer<IClientServiceRequest, Message
             message.ThreadId = singleDraftRequest.Item.ThreadId;
         }
 
+        // Local draft mapping header must never leak to recipients.
+        singleDraftRequest.Request.Mime.Headers.Remove(Domain.Constants.WinoLocalDraftHeader);
+
         singleDraftRequest.Request.Mime.Prepare(EncodingConstraint.None);
 
         var mimeString = singleDraftRequest.Request.Mime.ToString();

Wino.Core/Synchronizers/OutlookSynchronizer.cs

@@ -1812,6 +1812,10 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
                 {
                     await HandleFailedResponseAsync(bundle, response, errors);
                 }
+                else
+                {
+                    await HandleSuccessfulResponseAsync(bundle, response).ConfigureAwait(false);
+                }
             }
         }
 
@@ -1859,6 +1863,39 @@ public class OutlookSynchronizer : WinoSynchronizer<RequestInformation, Message,
         }
     }
 
+    private async Task HandleSuccessfulResponseAsync(IRequestBundle<RequestInformation> bundle, HttpResponseMessage response)
+    {
+        if (bundle?.UIChangeRequest is not CreateDraftRequest createDraftRequest)
+            return;
+
+        try
+        {
+            var content = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
+            if (string.IsNullOrWhiteSpace(content))
+                return;
+
+            var json = JsonNode.Parse(content);
+            var createdDraftId = json?["id"]?.GetValue<string>();
+            if (string.IsNullOrWhiteSpace(createdDraftId))
+                return;
+
+            var createdConversationId = json?["conversationId"]?.GetValue<string>();
+            var localDraft = createDraftRequest.DraftPreperationRequest.CreatedLocalDraftCopy;
+
+            await _outlookChangeProcessor.MapLocalDraftAsync(
+                Account.Id,
+                localDraft.UniqueId,
+                createdDraftId,
+                createdConversationId,
+                createdConversationId).ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            // Draft mapping is best-effort here. Delta sync mapping remains as fallback.
+            _logger.Debug(ex, "Failed to map Outlook draft from create-draft response.");
+        }
+    }
+
     private void ThrowBatchExecutionException(List<string> errors)
     {
         var formattedErrorString = string.Join("\n",