[Dovecot] help writeing rule for preventin spam

[Sophia Alikhani]

Hi
I installed qmail-jms1-7.07 + domainkey-patch + simscan + clamav+
dovecot-1.1.7+ vpopmail+ spamassassin
I also used Bayes + AWL as database connection in local.cf
I don't know how can i stop these type of spam at MTA level (qmail) i
wrote a rule in .dovecot.sieve
if header :contains ["From","To"]
           ["%u at mydomain]
 {
   discard;
   stop;
 }
In the real i nedd to stop any mail from a virtual user to him/her self.
-- 
with regards
Sophia Alikhani
WorkPhone: +98-21-8497057
Mobile : +98-912-3361036