On Dec 23, 2019, at 11:34 AM, Hector Santos
I agreed and I have admitted I have a single rule for comparing the
ip-literal with the connection IP. Mismatches are rejected. There are some
cases (MUA behind the NAT) where there are a FP, resolved with authentication
requirements. I believe this test is a correct technical SMTP check compared
to a subjective, nondeterministic conclusion to block all ip-literals that
technically violates SMTP.
I believe that NATs within the ipv4 network (not merely on the periphery) will
become increasingly commonplace, for as long as there is a public ipv4
Internet. I also believe that the HELO/EHLO tag is really only usable for
inclusion in Received fields and to identify the client system within its own
environment. So any checks on validity with respect to the server environment
are dubious at best and may do harm to the protocol. This applies equally to
IP address literals and names.
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