--On Sunday, June 05, 2011 05:56 +0000 John Levine
So scrutinizing page 60 of RFC 5321, I see a list of opt-info
clauses which offers Additional-Registered-Clauses. So I
propose a port clause, like this:
Received: from vance3.state.gov (vance.state.gov
[188.8.131.52]) by mail1.iecc.com ([184.108.40.206])
with ESMTP via TCP port 1234 id 2467626873; 03 Jun 2011
Received: from cl-t108-372cl.privatedns.com
([2607:f748:1200:fa:230:48ff:febd:a370]) by mail6.iecc.com
([2001:470:1f07:1126::5370:616d:6d79]) with ESMTP via TCP
port 1234 id 2467293036; 28 May 2011 16:18:48 -0000
There is a registry for Additional-registered-clauses, which is
currently empty, but we could fix that. Seems reasonable?
Yes. I don't have a strong opinion about whether there should
be two port keywords or one with a syntax that could be used to
record one, the other, or both.