I just found out that when using deliver or saving mails with IMAP APPEND command there was all kinds of race condition bugs that could cause e.g.:

dovecot-uidlist: Duplicate file entry at line 18: 1241457213.M690227P32531.host,W=3359:2,T (uid 170019 -> 170020)

And who knows what else.

If you've run into those problems, these patches should help:

http://hg.dovecot.org/dovecot-1.1/rev/6bbe27c32cb8 http://hg.dovecot.org/dovecot-1.1/rev/003bebac2c76 http://hg.dovecot.org/dovecot-1.1/rev/96c8632775df

They are pretty large though, hopefully won't break anything. But at least my stress tests can no longer break it. I'll probably release v1.1.15 RC in a few days so at least some people can try to break it before the final v1.1.15 :)