bug#30347: smtpmail.el doesn't retry with authentication when greylisting is used

[Robert Pluim <rpluim@gmail.com>]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> writes:
>
>> I've long been dealing with the following problem: I'm using GNU Emacs
>> (current 26.0.91, but the problem has existed for a long time before
>> that) and Gnus to send mail.  The relaying MTA uses greylisting when
>> receiving mail for local accounts without authentication, but
>> smtpmail.el cannot deal with the resulting temporary SMTP codes.  I'd
>> expect that it would retry with authentication, but doesn't.
>>
>> I've used the following snippet to fix this.  Perhaps this (or something
>> similar) can be used to fix this issue?
>
> Hm...  Well, the SMTP error message you're getting is "450, Requested
> mail action not taken: mailbox unavailable."?  Retrying with a password
> seems a bit odd in that instance.  On the other hand, if this is the
> common way for SMTP servers to say that "we're greylisting; log in
> first" then it would be OK anyway.
>
> But is it?  :-)

Itʼs one of the ways. Some return 451 instead. Some 421. Itʼs all very
fuzzy :-)

Oh, and thereʼs an official 'authentication is required' code whose
value escapes me for the moment.

BTW, if emacs has credentials for the connection itʼs making, would it
not make sense to attempt authentication before delivery?

Robert