out of place mx records.

[Fr34k]

----- Original Message ----
> From: Mark Andrews <marka at isc.org>
> To: Barry Margolin <barmar at alum.mit.edu>
> Cc: comp-protocols-dns-bind at isc.org
> Sent: Thu, October 28, 2010 9:49:46 PM
> Subject: Re: out of place mx records.
> 
> 
> In message <barmar-ED15C5.21262028102010 at news.eternal-september.org>,  Barry 
>Mar
> golin writes:
> > In article <mailman.585.1288263412.555.bind-users at lists.isc.org>,
> >   Tony Finch <dot at dotat.at> wrote:
> > 
> > > On  Thu, 28 Oct 2010, Gregory Machin wrote:
> > > >
> > > > My  question is why would "IN    MX    10     mcvpemr01" and "IN    MX
> > > >  10     mcvpemr02" be repeated trough the zone file surely this is
> > > >  redundant ?
> > > 
> > > Some hostmasters like to ensure that mail  is not directed to hosts that 
do
> > > not listen on SMTP. They prefer  misdirected mail to be rejected
> > > immediately rather than waiting  days for the sending system to time out.
> > > Some of my colleagues have  this setup on the zones they manage
> > > (eng.cam.ac.uk and  cl.cam.ac.uk).
> > 
> > But configuring MX records won't necessarily  accomplish this.  It will 
> > cause mail for all these hosts to be  delivered to mcvpemr01 or mcvpemr02.
> 
> And they can do a SMTP level  rejection rather than waiting for the
> sending server to abandon sending the  email due to multiple timeouts.
> Just return 550 for all mail directed to  users at those hosts.   It
> would be nice if we could standardise a MX  target of "." as saying
> that this domain doesn't accept email e.g. "MX 0 ."  the same way
> as "SRV 0 0 0 ." means that there is no service for the  named
> protocol.  That way the sending MTA or the MSA can reject the  email.
> 

Hello,

Is there an advantage to process email just to have the destination MX reject 
it?

Why not use " IN MX 100 localhost" so the email doesn't even leave the source?

Or, am I confused?


> Every time it get suggested people shoot it down worrying  about
> private nets that have addresses at "." or get worried about  thousands
> of machines making A/AAAA queries for "." where the MTA  doesn't
> check that the MX target is a valid host name.
> 
> Mark
> -- 
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117,  Australia
> PHONE: +61 2 9871 4742                  INTERNET: marka at isc.org
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