cyrus-imap 2.5.3 - `lost' messages

[Dirk-Willem van Gulik]

On a smal cyrus imap 2.5.3 setup (freebsd ports, default settings, 5k 
users, 300 Gb mboxes) we are seeing very sporadic `loss' of messages (once 
every few months; 1 or 2 messages; out of a few 100k to a million going 
through perfectly fine in the same period).

They disappear; but are still present as a /var/spool/imap/user/X/12345.
  files.

But cannot be found; even when searching through IMAP on 
message-ID or otherwise unique elements. Searches in the same veign for 
the messages before/after the lost one work and return those.

A grep through the cyrus.index shows its unique message ID.

A full  reconstruct with /-r/-R/-G does not seem to bring it back as 
visible.

The mesaages lost are otherwise normal; fully valid mime; and when
re-injected - pass through and surface.

What is the right way to debug this ? We suspect it may have something to 
do with either (al)pine and thunderbird; as it seems to hit users that mix 
those two clients - during periods they use both. All else seems normal.

Thanks,

Dw.