Improving thread mapping for all synchronizers.

Wino.Core.Domain/Interfaces/IMailService.cs

@@ -131,6 +131,12 @@ public interface IMailService
     /// <returns>Draft MailCopy and Draft MimeMessage as base64.</returns>
     Task<(MailCopy draftMailCopy, string draftBase64MimeMessage)> CreateDraftAsync(Guid accountId, DraftCreationOptions draftCreationOptions);
 
+    /// <summary>
+    /// Finds a mail copy in the given account by RFC Message-Id.
+    /// Returns null when no local match exists.
+    /// </summary>
+    Task<MailCopy> GetMailCopyByMessageIdAsync(Guid accountId, string messageId);
+
     /// <summary>
     /// Returns ids 
     /// </summary>