Log on v2.49.1 is flooded with messages similar to:
2026-05-14T12:34:56.789Z core/event WARNING "" 26 "src/download.rs:286: Failed to download message rfc724_mid=...@localhost: IMAP location for \"...@localhost\" post-message is unknown."
I think the problem might have been triggered by the mailbox filling up between receiving the pre-message and the post-message or that the larger post-message was cleaned up sooner than the pre-message on the chatmail server. A message for the same rfc724_mid is repeated every few milliseconds for quite a few times, then does it again after 20 seconds or so. This may also be wasting quite some CPU and network (?) throughput along with log storage.