On Fri, Jun 10, 2011 at 05:00:16PM +0200, Wiebe Cazemier wrote:
> ----- Original Message -----
> > From: "Wietse Venema" <[email protected]>
> > To: "Wiebe Cazemier" <[email protected]>
> > Cc: [email protected]
> > Sent: Friday, 10 June, 2011 2:50:34 PM
> > Subject: Re: unverified_recipient_tempfail_action = permit
> >
> > Wiebe Cazemier:
> > > - The server is backup MX for mail hosts that I don't know anything
> > > about.
> >
> > In that case, the backup MX needs to ask the primary MX if the
> > recipient is valid. Otherwise, you become a backscatter source.
> >
> > Wietse
> >
>
> But how can it do that when the primary server is down and while not
> deferring the incoming request?
It can't. Never before seen recipients will be deferred, recipients
validated while the primary MX was up and cached (for 7-14 days) will
however be accepted. This is good enough, and the best you can do
without getting a recipient feed from the primary MX host.
--
Viktor.
