Valdis(_dot_)Kletnieks(_at_)vt(_dot_)edu wrote:
(Am cc'ing the IETF-SMTP list, hopefully it's alive and somebody there
will have guidance on this... For the IETF-SMTP list, the discussion is
what to properly do if handed this during an SMTP transaction:
MAIL FROM:<user(_at_)domain(_dot_)name@other.domain>
Sendmail currently issues a '250 OK'.
I think it is a valid address. It was manually routed from one
domain to another. I used that feature a few years ago to
stop spam as a result of people scanning net-news postings.
(I posted with x(_at_)y@z). Any email that came to that address
at domain 'y' would get extra filters before relaying to domain 'z'.
It is another way of doing mail relaying.
I did an exhaustive search a few years ago. The ability to
route with multiple '@' was in an RFC, so it is valid.
(If it has not been superseded).
Set mail relay to off, if you can. (I don't know the exact keyword).
It should stop working.
-Doug