Vexim and Fetchmail?

Hi there,

I've got a questions about spamassin in combination with vexim and 
fetchmail.
I created a fetchmailrc which receives Emails from another Mailbox and 
forwards them to my Emailadress using Vexim. The mail gets delivered 
with no Problem but there is no Spamscanning done. Does this happen 
because the Emailaddress the email is sent to is nowhere in my mysql 
database?
The Adress is not rewritten but just locally forwarded to my mailbox.


thanks in advance,
regards

Sebastian