One of my client received emails from ISP saying the SPAM email generated from their network with PIX outside ip. We want to disable the outbound SMRP (port25) on the firewall, so that the emails will be stopped. PIX config has 'no fixup protocol smtp 25'.
Is there any way I can use the fixup to block the outbound SMTP (without impacting any other services)
or do I need to create a ACL for port25 and apply on the inside interface..?