fix: dedup by message_id in imap_sync_folder — stop deleted mails reappearing from Trash

- imap_sync_folder now checks message_id in addition to (folder_id, imap_uid)
- If mail was moved to Trash by IMAP server (new UID, same message_id), it is recognized
- Soft-deleted mails with matching message_id are skipped, not re-created
- Prevents deleted mails from reappearing when IMAP server moves them to Trash

app/plugins/builtins/mail/services.py

@@ -635,10 +635,41 @@ async def imap_sync_folder(
                 )
             ).scalar_one_or_none()
 
+            # Also check by message_id — mail may have been moved to Trash by IMAP server
+            if not existing_mail:
+                # Fetch headers first to get Message-ID
+                fetch_hdr = await client.uid('fetch', uid_str, '(BODY.PEEK[HEADER.FIELDS (MESSAGE-ID)])')
+                hdr_raw = None
+                for line in (fetch_hdr.lines if hasattr(fetch_hdr, 'lines') else fetch_hdr):
+                    if isinstance(line, bytearray):
+                        hdr_raw = bytes(line)
+                        break
+                if hdr_raw:
+                    hdr_msg = message_from_bytes(hdr_raw)
+                    peek_msg_id = hdr_msg.get("Message-ID", "")
+                    if peek_msg_id:
+                        existing_mail = (
+                            await db.execute(
+                                select(Mail).where(
+                                    and_(
+                                        Mail.account_id == account.id,
+                                        Mail.message_id == peek_msg_id,
+                                        Mail.tenant_id == tenant_id,
+                                    )
+                                )
+                            )
+                        ).scalar_one_or_none()
+
             if existing_mail:
                 # Don't touch soft-deleted mails — they're being deleted via sync queue
                 if existing_mail.deleted_at is not None:
                     continue
+                # Update folder_id and imap_uid if mail moved to a different folder
+                if existing_mail.folder_id != folder.id:
+                    existing_mail.folder_id = folder.id
+                    existing_mail.imap_uid = uid_str
+                elif not existing_mail.imap_uid:
+                    existing_mail.imap_uid = uid_str
                 continue
 
             # Fetch and parse the email