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Re: RFC 5321bis / 2821ter

2009-01-23 08:22:28

At 22:46 22-01-2009, John C Klensin wrote:
However, I had a discussion early this week with someone
interested in the slightly-fuzzy text about arguments to HELO
and/or EHLO and their relationship to spam-fighting.  The
discussion leads to a question, especially since 5321bis is our
first opportunity to really do something significant.

Question: Is it time to formally deprecate 821 and, in
particular, the main feature that distinguishes it: the use of
HELO by SMTP clients?  We would still need to require that SMTP
servers accept it, but we would tell full-capability clients
(including the client side of relays and gateways) that HELO is
obsolete.  One corollary of this is that we'd be telling
low-capability clients, particularly those that are part of MUA
systems, that they should be talking to Submit ports, not SMTP

RFC 2821 obsoletes RFC 821. There is a reference to RFC 821 in RFC 2821 and RFC 5321 for some features not in significant use today. The service extension model has been around for over seven years and the major MTAs have implemented RFC 2821. RFC 2821 specifies that servers MUST support the EHLO command even if they do not implement any specific extensions and clients SHOULD preferentially utilize EHLO rather than HELO with a fallback to HELO.

I don't know how much work it would be to formally depreciate RFC 821. It seems the right time to look into it. I still see traffic from SMTP clients which use HELO. I don't have a strong view about whether HELO should be obsoleted or not.

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