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Re: [ietf-smtp] Endless debate on IP literals

2020-01-02 13:10:57
On 1/2/20 1:07 PM, Dave Crocker wrote:

The target documents would be:

   1) Astreamlined rfc5321bis

yes.   But I don't think this is the place to impose policy, including policy about whether domain literals are permitted in EHLO/HELO.   I think this document should be targeted toward implementors of the protocol engines, with policy a separate layer (and probably in a separate document).   That way, implementors of the protocol engines have one clear and stable reference to work from.    Policy recommendations are less likely to be stable, as conditions will continue to change.   Putting policy recommendations in a separate document lets those recommendations evolve without affecting the base SMTP protocol specification.

So the SMTP protocol could permit IP address literals in EHLO/HELO as a matter of syntax, whereas policy could restrict that further.

   2) A document specifying requirements for Exterior MTAs, which would include mandating rfc5321bis, starttls, ...

I suspect the document needs to specify requirements for relaying across domain boundaries rather than talking about particular kinds of MTAs.  I'm not sure that there is, in practice, a clean separation between Exterior MTAs and Interior MTAs, such that only Exterior MTAs are involved in relaying across domain boundaries.


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