Slightly OT - MX RR Santity Check requested...

Mark Andrews Mark_Andrews at isc.org
Thu Mar 29 02:30:11 UTC 2007


> 
> > In article <euf4o6$98o$1 at sf1.isc.org>,
> >  Mark Andrews <Mark_Andrews at isc.org> wrote:
> > 
> > > > You mean "their" configuration is broken?  The sending mail server is N
> OT
> >  
> > > > ours.  We're on the receiving end.  
> > > 
> > > 
> > > 	No.  Your configuration is broken.  The lowest preference
> > > 	MXs MUST always be reachable.  You cannot depend upon
> > > 	fallback to higher preference MXs.  The sending side is not
> > > 	required to try them.  It is required to try all the lowest
> > > 	preference MXs.
> > 
> > RFC 2821 seems to contradict you:
> > 
> >    When the lookup succeeds, the mapping can result in a list of
> >    alternative delivery addresses rather than a single address, because
> >    of multiple MX records, multihoming, or both.  To provide reliable
> >    mail transmission, the SMTP client MUST be able to try (and retry)
> >    each of the relevant addresses in this list in order, until a
> >    delivery attempt succeeds.  However, there MAY also be a configurable
> >    limit on the number of alternate addresses that can be tried.  In any
> >    case, the SMTP client SHOULD try at least two addresses.
> 
> 	This does not cover how the list of addresses is choosen.
> 	RFC 952 still applies.  The list of addresses can legally
> 	be those of just the lowest preference MXs.

	Opps. RFC 974
 
> > -- 
> > Barry Margolin, barmar at alum.mit.edu
> > Arlington, MA
> > *** PLEASE post questions in newsgroups, not directly to me ***
> > *** PLEASE don't copy me on replies, I'll read them in the group ***
> > 
> > 
> -- 
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org



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