[Dovecot] OS X Mail.app 2 (Tiger) + dovecot -> new mail count doubled

Hello,

I've noticed a strange bug with Mail.app 2 (from OS X.4) and dovecot,
and I'm trying to identify where it comes from. I have a bunch of
mailboxes that can receive new mail (delivered by procmail) and I
have Mail set up as to automatically synchronize all maiboxes. When I
start up Mail, the count for new mail is doubled in every mailbox
that I have not seen yet. Looking at a mailbox restores the correct
count (mail is not actually duplicated, it's just the new mail
counter that is wrong).

Has anyone else seen this? Would this bug be from Mail.app or from
dovecot? (I suspect the former.)

Thanks a lot,

Alan Schmitt