I'd like to put a rule in place on our ASA that will drop any incoming SMTP traffic that has a FROM address matching our domain. For example, drop any inbound SMTP traffic that has a from address of [email protected]. However, I'm really unsure how to do this. Are there any articles or an overview that someone can point me to?
I'm interested in doing this as I believe it will help drop spoofed email traffic at the edge, before it even hits our antispam device.