--On Tuesday, September 02, 2014 14:30 -0400 John R Levine
<johnl@xxxxxxxxx> wrote:
>> Sadly, though it is very late in the process, I failed to
>> notice this originally, and must belatedly report a
>> significant issue noted by Wietse Venema. The response code
>> for rejecting a recipient with a nullmx domain and a sender
>> with a nullmx domain are reversed in the draft.
>>
>> Since 521 like 221 and 421 leads to connection drop after the
>> reply,
>
> Only when it's the SMTP greeting. In this case it's not.
> That suggests that JCK's suggestion to have a new RFC to
> replace 1846 is a good one, since it could mention this other
> fairly obvious use case.
See draft-klensin-smtp-521code. If additional text is needed
there, please suggest some.
>> it is only appropriate when the entire envelope will be
>> rejected. Thus 521 goes with rejection of a nullmx sender
>> domain and 550 with a particular nullmx recipient.
>
> No, 550 to reject the MAIL FROM is correct. See RFC 5321, sec
> 3.3. It's a policy rejection.
Yes, or 554, see Section 3 of draft-klensin-smtp-521code for
discussion (and, if I got that wrong, this would be a good time
to discuss it).
john