[Dovecot] Converting from qpopper mbox to dovecot maildir

[Dimos Alevizos]

Joseph Tam <jtam.home <at> gmail.com> writes:

> 
> On Tue, 5 Jul 2011, list <at> airstreamcomm.net wrote:
> 
> >> I didn't do anything special other than to use
> >>
> >>  	pop3_reuse_xuidl = yes
> >>
> >> so that clients don't re-download all their messages.
> >
> > Did you convert the mbox emails to maildir format as well, or just put
> > dovecot in front of the mbox files and run with the config setting you
> > described above?
> 
> No, I left the mailboxes as mbox and did not convert to maildir.  I had
> all sorts of mail clients and some use direct file access to their
> mailbox, so it requires a lot more deep-think before I can contemplate
> moving to maildir.
> 
> Many people on this list have successfuly migrated to maildir so I don't
> think you'll have too much trouble.
> 
> You'll appreciate that dovecot avoids some of the problems I had with
> qpopper:
> 
>  	- qpopper made temp copies of a user's INBOX, and if you didn't put
>  	the drop copy on another filesytem, you essentially halved a user's
>  	quota.
>  	- because of the above, qpopper eats I/O like candy.
>  	- multiple client qoppper access will trouncing/locking user INBOXs.
> 
> Joseph Tam <jtam.home <at> gmail.com>
> 
> 

We recently completed the migration in our company from qpopper/mbox to
dovecot/mbox using only pop3_reuse_xuidl = yes and while everything went much
easier than we feared we came across an interesting problem that you might want
to pay attention to.

We use dovecot to provide both pop3 and imap (directly and via webmail) access
to our client's mailboxes and we noticed that when a client moves a mail to a
different folder and then back into INBOX (say he deleted it by mistake and
moves it back), dovecot inserts the same X-UIDL into it's cache, thus creating
duplicate entries.

When a pop3 client sees this (at least outlook in our case) it think's that
there's something wrong with the server's X-UIDL handling and re-downloads the
duplicate messages. EVERY time the user checks his mails.

We're still in the middle of troubleshooting this, but I believe deleting
dovecot's cache would solve the problem for a particular mailbox, but I can't
think of anything that would solve it permenately.

Dimos Alevizos