[Dovecot] POP users complaining about multiple copies of mail

[Timo Sirainen]

On Tue, 2010-11-16 at 17:40 +0000, Timo Sirainen wrote:
> I've heard it several times, and it's always been Outlook. It just seems
> to go nuts when server changes. No one who has complained about this has
> ever come back to say if they managed to fix it somehow.
> 
> My guess: recreate the account in Outlook and hope for best.

Oh, the other possibility of course: You seem to be using mbox format?
If the message's IMAP UIDs change, the POP3 UIDL changes and the
messages get redownloaded.

You should at least explicitly set mail_location setting so Dovecot
doesn't use autodetection. Also look for Dovecot errors in log file.