[Dovecot] POP3: Message ordering changed unexpectedly

[Timo Sirainen]

On 3.2.2014, at 17.19, Gedalya <gedalya at gedalya.net> wrote:

> I think I'm having a problem with simultaneous pop3 connections on the same mailbox with one connection deleting a message.
..
> Jan 29 14:36:33 imap1 dovecot: pop3(riki at domain.com): Error: Message ordering changed unexpectedly (msg #1: storage seq 1 -> 2)
> Jan 29 14:36:33 imap1 dovecot: pop3(riki at domain.com): Disconnected: POP3 UIDLs couldn't be listed top=3/2662, retr=0/0, del=0/1227, size=51548362
> 
> Running Dovecot 2.2.10+hg-6018854c8c91
> Mailboxes were migrated recently using dsync with pop3 migration plugin.

What mailbox format is this with? I can only reproduce this by forcibly making sure that pop3.order field doesn't go into dovecot.index.cache field. Anyway .. this should help: http://hg.dovecot.org/dovecot-2.2/rev/59decc957b39

So also add something like "uidls=%u" to your pop3_logout_format. This will use up a little bit more memory by storing all the UIDLs in memory. The %u output can sometimes be used to debug why POP3 clients are redownloading messages.