-----Original Message-----
From: owner-ietf-mxcomp(_at_)mail(_dot_)imc(_dot_)org
[mailto:owner-ietf-mxcomp(_at_)mail(_dot_)imc(_dot_)org] On Behalf Of Jon Kyme
Sent: Friday, April 23, 2004 12:02 PM
To: ietf-mxcomp(_at_)imc(_dot_)org
Subject: Re: RE: Can you ever reject mail based on RFC2821 MAIL FROM?
publisher says something like:
"mydomain.example.com: only nnn.nnn.nnn.nnn applies_to 'MAIL FROM'
# we know this means our mail might not be forwarded # but
we're OK
with that.
Sorry, Jon, that won't work.
Suppose alice(_at_)mydomain(_dot_)example(_dot_)com sends mail to
bob(_at_)alumni(_dot_)almamater(_dot_)edu(_dot_) But bob has set up
forwarding of
bob(_at_)alumni(_dot_)almamater(_dot_)edu to bob(_at_)company(_dot_)com
Harry, it breaks forwarding. We know. In the example I gave
you at your
request: The publisher knows; a legitimate sender must know;
the recipients should know.
Please do me the courtesy of reading what I've written (and
accept my apologies if I didn't make it clear). I don't
believe it's a terribly obscure point that I'm trying to make.
Now company.com does the check of MAIL FROM and erroneously
rejects the
mail because it is coming from alumni.almamater.edu's MTA
which has the
wrong IP address.
QED
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.
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?
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.
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."
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?