How to prevent being a 'bouncer' of evil mail?
How can I prevent boucing 'evil' messages?
For spammer viruses, one could just employ an anti-virus and set it
not to bounce.
But for other messages, what can I do?
In one of my implementations, I have a gateway that filters messages,
removing most spam and viruses, than redirect them to the appropriate
servers. Thus, I do not have a record of user accounts for those
domains. What usually happens is that I get messages for
"email@example.com", from "firstname.lastname@example.org", and after the final
server gets the message, it bounces to yahoo.
I don't want to cause any trouble to other admins. I understand the
way that smtp works, and that I must issue DSN's for undelivered
messages. But is there any mixture of techniques to avoid bugging
yahoo or other servers? Or have I missed the idea of DSN's?
I think this have been discussed before, but signing messages is not
enough, is it?
The only think I could think now is SPF greylisting (~all) from yahoo.