* Henning Brauer  [2007-05-23 11:48]:

quoted text
> * Bob Beck  [2007-05-22 23:45]:

> > > just deduced from trial and error. Also greylisting should happen at

> > > RCPT TO, and probably not at DATA as there are some widely used MTAs

> > > that are buggy and choke when a 4xx error is sent in the DATA phase.

> >

> > 	I've been running this at DATA for months, and not seen any

> > issues with it.

> >

> > 	anyone here got hard evidence of such bugs - please show

> > me. Or is this just uninformed speculation?

>

> err, wait, are you giving a 4xx in reply to DATA?

> that is invalid.

eh, I wanted to send that in private mail.. too late ;(
rfc 2821 specifically forbids this behaviour.


The DATA command can fail at only two points in the protocol exchange:
   -  If there was no MAIL, or no RCPT, command, or all such commands

      were rejected, the server MAY return a "command out of sequence"

      (503) or "no valid recipients" (554) reply in response to the DATA

      command.  If one of those replies (or any other 5yz reply) is

      received, the client MUST NOT send the message data; more

      generally, message data MUST NOT be sent unless a 354 reply is

      received.
   -  If the verb is initially accepted and the 354 reply issued, the

      DATA command should fail only if the mail transaction was

      incomplete (for example, no recipients), or if resources were

      unavailable (including, of course, the server unexpectedly

      becoming unavailable), or if the server determines that the

      message should be rejected for policy or other reasons.


--

Henning Brauer, hb@bsws.de, henning@openbsd.org

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