[NNTP] Snapshot 4

[Kai Henningsen]

clive at demon.net (Clive D.W. Feather)  wrote on 03.12.04 in <20041203160725.GD21270 at finch-staff-1.thus.net>:

> Ken Murchison said:

> > I think most other
> > protocols also discourage deriving meaning from any initial greeting
> > text (except for SMTP's <domain> param and ad-hoc ESMTP token).
>
> And in SMTP that's not listed as free-form text, it's specific syntax.

This sounds rather confusing.

There's exactly one place in RFC 2821 where the string ESMTP is used  
outside generic text, and that is in the content of Received: lines (as a  
protocol value). That has exactly zero use for the actual message exchange  
protocol.

There's a myth going around about putting ESMTP into the 220 greeting  
line. There's never been such a rule. In fact, such a rule was discussed  
and rejected.

There's the EHLO command that a new client sends instead of HELO, always  
prepared to fall back to HELO if EHLO doesn't work; this command is also  
the CAPABILITIES command of SMTP.

The 220 greeting does have a single specified parameter, the server's  
domain name; it's specified by position just like, say, the answer to the  
GROUP command in NNTP. In fact, it's been that way since RFC 772  
(September 1980), the first draft of this new "MAIL TRANSFER PROTOCOL"  
that was to replace mail-via-FTP, before even HELO was invented. (They  
also had a baroque MRSQ "Mail Recipient Scheme Query" that was supposed to  
negotiate the sequence in which text and recipients were communicated.  
Hey, protocol negotiation in the very first draft!)

MfG Kai