Re: [ietf-smtp] parsing SMTP replies (was: Proposed ESMTP keyword RCPTLIMIT}

Ned Freed <ned.freed@mrochek.com> Fri, 19 March 2021 15:35 UTC

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Date: Fri, 19 Mar 2021 07:52:57 -0700 (PDT)
From: Ned Freed <ned.freed@mrochek.com>
In-reply-to: "Your message dated Wed, 17 Mar 2021 22:39:48 -0400" <7d448367-d5a0-7baf-3df4-dcafe1859437@network-heretics.com>
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To: Keith Moore <moore@network-heretics.com>
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Subject: Re: [ietf-smtp] parsing SMTP replies (was: Proposed ESMTP keyword RCPTLIMIT}
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> On 3/17/21 9:37 PM, Sam Varshavchik wrote:

> >
> > I believe that the generally good track record of historical
> > interoperability of SMTP implementations goes back to what's in
> > section 4.5.3 of RFC 821, that gives the minimal limits of various
> > things, like line lengths. And, incidentally, the minimum number of
> > recipients that an SMTP server should accept is 100 recipients.

> It's been a long time but I'm pretty sure I've seen situations in which
> it made sense for the recipient limit to be 1.   For example: a
> special-purpose device (e.g. email to fax, email to printer) or a
> gateway to a dissimilar mail system, or anything for which it makes
> sense to insist that per-recipient errors get immediately reported to
> the client.

Some do this, others accept any number of RCPT TOs and ignore them all. It
depends on whether the the RCPT TO actually contains any information.

This reminds me that this specification needs to cover message submission. Will
add.

				Ned