Curbing Image/PDF spam : Realtime Black Lists
Another way of fighting images spam is by Realtime Black List lookup. This tactic is probably one of method which is inexpensive to server resource.
With postfix, you could just add reject_rbl_client images.rbl.msrbl.net to smtpd_client_restrictions section of postfix’s main.cf.
For instance:
smtpd_client_restrictions = permit_mynetworks,
reject_rbl_client images.rbl.msrbl.net,
….
For qmail, you could just add -r images.rbl.msrbl.net as tcpserver option of your qmail smtp startup script.
Note : images.rbl.msrbl.net - Hosts found sending mail contaning spam images. Check out MSRBL for more info.
