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RE: RE: Can you ever reject mail based on RFC2821 MAIL FROM?

2004-04-23 15:22:44

Jon Kyme:
No.
This is not erroneous. It's in accord with the published
record and with the final recipient system policy. It's correct.
Try again.


--Harry Katz <hkatz(_at_)exchange(_dot_)microsoft(_dot_)com> wrote:
So just to make sure I understand correctly, under the policy you've
defined, the sender is essnetially giving permission to receivers to
reject mail if the MAIL FROM domain fails to be validated, right?


YES.


But senders have absolutely no knowledge about what forwarding
relationships the recipients may have set up.  Thus, they have no way to
know whether or not their messages will be accepted or rejected under
this policy.

Correct, the sender will get a bounce in this case saying the message could not be delivered.


In other words, the policy you've stated is equivalent to "We're sending
mail from this set of IP addresses.  We don't really care whether they
get delivered or not."

Not necessarily. It's the responsibility of any mailer accepting the message to either deliver it or return it. If the sender and receiver are both using LMAP-MAIL-FROM, AND the forwarder doesn't rewrite, AND the receiver didn't whitelist the forwarder, THEN the message is returned to sender.


Other than spammers themselves, who would be willing to make such a
policy statement?  And if a domain IS willing to make such a policy
statement, why shouldn't the receiver just reject ALL mail coming from
that domain?


Not sure why this is a hard concept. Perhaps you could explain what directOnly is for and I can replace some key words and give you back the explanation you are seeking.


In general, an MTA should either be an agent for the sender, or an agent for the receiver. Third-party MTAs don't get involved just on a whim; either the sender or the receiver asked for them to be involved. If a receiver wants to receive forwarded mail, the forwarder needs to comply, or they need to make an exception for that forwarder.

--
Greg Connor <gconnor(_at_)nekodojo(_dot_)org>


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