scanning the logs for occurrences of "error," I find:
# grep error dovecot* dovecot-info.log:Apr 15 17:01:09 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=, size=5887 dovecot-info.log:Apr 16 03:06:48 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<20150416100642.CA9C824764@host2.localdomain>, size=13237 dovecot-info.log:Apr 16 17:01:18 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=, size=5887 dovecot-info.log.0:Apr 14 13:24:07 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<CAFOe2y4AwkM_BnkGNssLKkXRFJRk1GoAo7y6T7igTwtFMQk28Q@mail.gmail.tld>, size=3033 dovecot-info.log.0:Apr 14 13:24:07 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<cf8d60100fb6d439c559221f00df2f37f80.20150414175622@mail100.atl31.mcdlv.net>, size=32589 dovecot-info.log.0:Apr 14 13:24:07 lda(user2@domain2.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<23233383_24761373-24761373@sbe203.redbeanforhealthopen.ninja>, size=6951 dovecot-info.log.0:Apr 14 13:24:07 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<93B38E8FD4B2741936862E3F@[10.0.248.3]>, size=2197 dovecot-info.log.0:Apr 14 13:24:07 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<4A13BE2E2FC7C49B7112BEE5@[10.0.248.3]>, size=4700 dovecot-info.log.0:Apr 14 13:29:07 lda(user2@domain2.tld): Info: copy from stdin: box=INBOX, uid=952044, msgid=<2361227557511242361114254436978565@ddxlohivv.errorsinvolved.tld>, size=6891 dovecot-info.log.0:Apr 14 13:34:07 lda(user1@domain1.tld): Info: copy from stdin: box=Bulkmail, uid=error, msgid=<1120736677264.1115884694416.1417834012.0.291256JL.1002@scheduler.constantcon..., size=44835 dovecot-info.log.0:Apr 14 13:34:07 lda(user1@domain1.tld): Info: copy from stdin: box=Bulkmail, uid=error, msgid=<cm.050532.qulthjk.jyntyklj.r@cmail20.tld>, size=42787 dovecot-info.log.0:Apr 14 13:34:07 lda(user2@domain2.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<63b529fb59de3613763afced1552234b_4334516_4774565@sbe213.proslimfitbody.ninja>, size=4407 dovecot-info.log.0:Apr 14 13:39:07 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<cec4d3a3384c6e714e89d33d4a113800-m511477@pfsense.org>, size=2941 dovecot-info.log.0:Apr 14 13:59:07 lda(user2@domain2.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<22304076-63b529fb59de3613763afced1552234b.63b529fb59de3613763afced1552234b@s..., size=4492 dovecot-info.log.0:Apr 14 17:01:08 lda(user1@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=, size=5887 dovecot-info.log.0:Apr 15 17:00:09 lda(user3@domain1.tld): Info: copy from stdin: box=INBOX, uid=error, msgid=<201504160000.t3G005Eu034535@brunch.is>, size=1762 dovecot.log.9:Apr 15 11:02:42 imap(user1@domain1.tld): Error: Log synchronization error at seq=3274,offset=152 for /mail/domain1.tld/user1//dovecot.index: Append with UID 302382, but next_uid = 2419524
Not a lot of errors, but not zero either.
-------- Original Message -------- Subject: Re: Dovecot 2.2.16: disappearing messages, mismatched summaries, duplicated messages, excessive full re-downloads From: Timo Sirainen <tss@iki.fi> To: David Gessel <gessel@blackrosetech.com> Date: Thu Apr 16 2015 21:31:30 GMT+0300 (Arabic Standard Time)
On 16 Apr 2015, at 04:45, David Gessel <gessel@blackrosetech.com> wrote:
My Dovecot 2.2.16 server is interacting poorly with a variety of mail clients. The symptoms include disappearing messages, mismatched summaries, duplicated messages, and excessive full re-downloads.
What were you running before Dovecot v2.2.16? An earlier Dovecot? A whole different system?
dovecot.log shows runs of this error: Apr 15 09:02:37 imap(user@domain.com): Warning: Maildir /mail/domain.com/user//.Sent: Expunged message reappeared, giving a new UID (old uid=306286, file=1429102024.M826331P1156.host,S=1678,W=1724:2,S)
or this error: Apr 15 10:04:00 indexer-worker(user@domain.com): Warning: Maildir /mail/domain.com/user//.Sent: Expunged message reappeared, giving a new UID (old uid=306803, file=1428785463.M645546P27215.host,S=5389,W=5442:2,S) .. The first entry in dovecot.log.0 is at Apr 15 10:00:12, and the last entry at Apr 15 12:00:13; Dovecot is logging 4,490 expunged message reappeared messages per hour. Note the server has 4 accounts set up and very limited traffic, so 4,490 per hour would seem like a lot of anything to be logged.
These really shouldn't be happening..