[Mimedefang] Blacklist vs Access_db

[Stefano McGhee]

Hello everyone,
	I have what should be a quick and easy one.  Adding items to the
access_db file allows sendmail to block messages based on the last relay
and actual To:/From: (if you use the Blacklist Feature).  SpamAssassin's
Blacklist From feature actually blocks on the envelope "From", right?  
	My goal is to use blacklist_from to stop spammers that use an
elevated MX record selection to route through my ISP instead of my primary
MX at our premises.  Sendmail can't seem to help me there.  Is the envelope
"From", what shows up in my mail client, what SpamAssassin blocks/filters
on?

Cheers,

Stefano