Re: [apps-discuss] Feedback on draft-moonesamy-smtp-ipv6-00

[Ned Freed <[e-mail]>]

> > -----Original Message-----
> > From: [e-mail] [mailto:[e-mail]] On Behalf Of Ned Freed
> > Sent: Tuesday, November 15, 2011 9:40 AM
> > To: Tony Finch
> > Cc: [e-mail]; [e-mail]
> > Subject: Re: [apps-discuss] Feedback on draft-moonesamy-smtp-ipv6-00
> >
> > The point in the dialogue at which the 4yz is returned can also be a factor.
> > It's one thing to retry on a different A after getting a 4yz host
> > temporarily unavailable response to EHLO; it's rather different to
> > retry a different A after getting a 4yz user is over quota response to
> > the final dot.

> I thought the theory was that you only try different As or lower-precedence
> MXs if you fail completely to make an SMTP connection.

That's *a* theory. It is not *the* theory. Plenty of MTAs - in fact it seems to
be a significant percentage of them - don't work this way. Some will move on to
other MXes even if the failure occurs during inside the actual transaction. (I
happen to think this last extreme is wrong, but that's *my* theory for how this
should be done; it's not prohibited by any standard I'm aware of.)

> That is, if you get any 4yz reply at all, you stop there and requeue; if you
> get any 2yz or 5yz reply at all, you're done.

I think a pretty good case can be made for trying secondary MXes when the
banner response is a 4yz.

				Ned