On Jul 27, 2004, at 9:05 PM, Douglas Otis wrote:
This jump to step 5 omits checks for From headers in the message.
Right. My eyes missed the Resent-From. Sorry.
The random-1(_at_)dup(_dot_)com could have been a local user, (it had the right
domain), but when relayed to a MTA with a list of valid users, the mail
was rejected as the local part 'random-1' was not valid. The MTA
second
to last in the chain, then bounces the message. This may allow
filtering, or if done by a backup MTA, the knowledgeable server is
expected to be out of service.
Why would the first MTA receiving for dup.com not just reject the
message?
-andy