Do you use maildrop, spamassasin, or any other filtering process with your qmail setup?
Have a look at
http://www.lifewithqmail.org http://www.qmail.orgWhich version of plesk do you have?
http://download1.parallels.com/Plesk/PPP9/Doc/en-US/plesk-9.2-email-users-guide/http://www.koansys.com/tech/sieve-server-side-mail-filtering-with-postfix-dovecotOne way is to alter the default delivery from what you have now, to the example in the postfix setup.
I have not looked at whether you can use the default delivery as '/usr/local/libexec/doveco
t/deliver
'
i.e. qmail-local will pass the message to '/usr/local/libexec/doveco
t/deliver'
for delivery to the mailbox.