[Dovecot] Little problem with dovecot using mbox format

[Jd]

Hi everyone, this is my first post on this mailing list.  I recently 
installed postfix+dovecot+fetchmail on OpenBSD for my dad's office.  
(dovecot is setup as an imap server using mbox).  Everything worked 
flawlessly...until now. 

I don't know why, but now some emails seem to de-double themselves.  For 
exemple, yesterday morning I printed out all the emails.  To my surprise 
30 minutes later, I received 60 'new'' emails.  But these 60 emails 
weren't new, they were all copies of emails I had printed out earlier.  
Some emails were repeated some 10-15 times.  Now we never got this kind 
of problem until recently.  Has anyone ever experienced this kind of 
problem?  If so how did you fix the situation?  Most responses I got 
from the openBSD mailing list was to use maildir format.  Any insight 
into this?

Thanks,

Jean-Daniel


BTW we don't get THAT much email, maybe 200 a day for that 1 account 
that seems to be acting weird now.