Re: [ietf-smtp] Possible contribution to moving forward with RFC5321bis SMTP

[Viktor Dukhovni <[e-mail]>]

> On Dec 27, 2019, at 1:42 PM, John C Klensin <[e-mail]> wrote:
> 
>> It seems that the -02 has not yet been uploaded, did you mean
>> for it to be already available?
> 
> Sorry... meant -01.  Been thinking about and working on -02 too
> much.   It should be up in the next couple of hours.

Thanks, I see it now.  Thanks for including the "552 -> 442" issue,
much appreciated.

I'd also like to see a similar placeholder for clarifying the semantics
of a "554" greeting.  Is the client expected to immediately bounce the
message, or look for a better MX host?  The spec is not clear and
implementations vary.

Past behaviour by some MTAs (returning a 554 banner under load) made
the second choice more appropriate, but I've not seen recent reports
of whether that's ongoing.

More recently some users are running into policy-based 554 greeting
rejects, and don't want to keep retrying message that will be
consistently rejected.

I'd like to know which is the expected client behaviour, and which
is a work-around for particular unexpected circumstances a client
may encounter.

-- 
	Viktor.