Re: [Exim] roadrunner broke my new toy..

Marc Haber <mh+exim-users@???> wrote:
> On Mon, 3 May 2004 15:18:11 +0200, Giuliano Gavazzi
> <eximlists@???> wrote:
>> BAD logic. If the recipient does not exist (and we are talking here
>> of incoming messages) you must reject it at SMTP time.
>
> Where is that MUST written down? If you're a secondary MX, you can't
> reject at SMTP time since you most probably do not have a list of
> valid local parts.

Best practice (by which I mean regularly-discussed rather than defined in a
BCP) is to only use a secondary MX when you can assure that it has a way of
knowing what are valid localparts in the target domain, and the same spam
and virus rejection policies as the primary. At which point it probably
becomes not a secondary but a parallel primary (as someone else mentioned
here only today). May as well let it deliver on to the destination itself.

It isn't a MUST as in an RFC. But it does make sense.

Peter