sa-learn on mailbox or not ?

[sasa]

Hi (I use spamassassin-3.0.4), I have tried this on my account where I send all 
spam mail then have arrived on other my accounts:

#sa-learn --spam --mbox  /var/spool/mail/spam-report
Learned from 18 message(s) (19 message(s) examined).

..but however also after this operation the same spam mail aren't stopped and 
delivered to my account!!
where I mistake ??
thanks.

        Salvatore.