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Re: rfc2821bis-01 Issue 14 Continuation of 222 greeting and Issue 15 syntax for multiline replies

2007-04-10 15:47:50

At 13:23 +0100 on 04/10/2007, Tony Finch wrote about Re: rfc2821bis-01 Issue 14 Continuation of 222 greeting and:

 >       Note: Unextended SMTP does not have any
       commands that allow this type of reply, and so does not have
       continue or abort commands.

I "believe" the last note had the intention to NOTE that 150 would be used as
 > a response that the client will REACT too.  The "Unextended
SMTP" implies they will be ignorant on how to react. i.e, an ESMTP spec might
 define this.

 However, it is still in play for normal 2821 operations.

Absolutely not. The sentence you quoted means that 1xy replies can only
occur if an extension is specified to use them. Without the server
offering an explicit extension and without the client explicitly
activating that extension, they cannot be used.

This is a question of semantics and definitions. Does "Unextended SMTP" mean a command that is capable of being issued due to occurring in the 220 reply to a EHLO connection or does it mean a session started with EHLO as opposed to HELO?

I think that we can agree that using HELO is the original SMTP Protocol. Using a EHLO EXTENDS this protocol so that you get a 220 list of EXTRA supported capabilities (most of which list commands that can be issued to extend the protocol but some of which by-themself provide the information needed for the extension [I think SIZE is such a 220 reply that tells the MUA the maximum acceptable message size]).

Thus the ability to accept EHLO can in-and-of-itself make an SMTP Server capable of being defined as using the/an "Unextended SMTP" Protocol (even if it does not return ANY command extensions in its 220 reply).

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