On Sat, 2006-05-20 at 17:43, Paul R. Ganci wrote:
Comment the: FEATURE(`accept_unresolvable_domains')dnl in sendmail.mc and you won't accept email with bad reply addresses.
As an aside, the original message is legitimate. My wife and I do Alaskan malamute dog rescue. The original message had rescue related material. I suspect the reply-to email address was just wrong in the sender's email client. It is unfortunate because I am sure the people believe we have blown them off, when in reality we just can't contact them.
That's why it's better to not accept it in the first place. If there are no intermediate relays the original sender will get the bounce from his own mailer to let him know about the problem.