[Dovecot] [OT] How is the Changelog file created?

[tom at replic8.net]

hi,

running dovecot-nightly on netbsd, just rebuilt for testing.
for quite some time now (about a month) i'm getting these:

==snip==
Feb 26 20:38:20 hostname imap(tom): Corrupted index file
/home/tom/Maildir/.INBOX/.imap.index: No unseen messages found with
first_unseen_uid_lowwater 25260, seen_messages_count 12, messages_count 18
==snap==

when this happens, my client is unable to display 'subject' and 'from'
anymore - as i'm using IMP (http://www.horde.org/org/) as webmailer
mainly i can't say it happens with other clients.

restarting dovecot doesn't change anything, i have to delete
.imap.index.* from maildirs files to get it working properly again.

i tried various cache settings and even disabled caching,
without any noticeable effect.

any hint? need more info?

--
many thanks for the good work,
TOM