I have a personal Postfix mail server set up that has been working fine for years. It's not very busy. A bunch of smtp_*_restrictions help it fight spam -- not a lot of spam gets through anymore. I have not set up a specific spam fighting solutions (ie, one of Spamassasin et al.) -- the restriction rules alone seem to be able to block most spam.
Some email addresses get forwarded to (mostly) Gmail mailboxes. The server has been getting a lot of replies from google, saying my server is forwarding spam messages.
What's happening, I think, is that Posfix is forwarding messages before applying all of the *_restrictions rules I've set up.
So the question is: how do I tell Postfix to apply all restrictions, even for mail that is not delivered to local mailboxes?