imap: avoid reconnection loop when message without Message-ID is marked as seen

- do not attempt to mark reserved meessages as seen when
  messages with empty Message-ID are marked as seen on IMAP
- do not reconnect on Seen flag synchronization failures This avoid
  reconnection loops in case of permanent errors in `sync_seen_flags`

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Fixes
+- avoid reconnection loop when message without Message-ID is marked as seen #3044
+
+
 ## 1.73.0
 
 ### API changes

src/imap.rs

@@ -1980,7 +1980,7 @@ async fn mark_seen_by_uid(
         .sql
         .query_row_optional(
             "SELECT id, chat_id FROM msgs
-                 WHERE rfc724_mid IN (
+                 WHERE id > 9 AND rfc724_mid IN (
                    SELECT rfc724_mid FROM imap
                    WHERE folder=?1
                    AND uidvalidity=?2

src/scheduler.rs

@@ -11,6 +11,7 @@ use crate::dc_tools::maybe_add_time_based_warnings;
 use crate::ephemeral::delete_expired_imap_messages;
 use crate::imap::Imap;
 use crate::job::{self, Thread};
+use crate::log::LogExt;
 use crate::smtp::{send_smtp_messages, Smtp};
 
 use self::connectivity::ConnectivityStore;
@@ -206,15 +207,11 @@ async fn fetch_idle(ctx: &Context, connection: &mut Imap, folder: Config) -> Int
             }
 
             // Synchronize Seen flags.
-            if let Err(err) = connection
+            connection
                 .sync_seen_flags(ctx, &watch_folder)
                 .await
                 .context("sync_seen_flags")
-            {
+                .ok_or_log(ctx);
-                connection.trigger_reconnect(ctx).await;
-                warn!(ctx, "{:#}", err);
-                return InterruptInfo::new(false);
-            }
 
             connection.connectivity.set_connected(ctx).await;