Re: Domain of sender address does not exist

[Brian Candler <B.Candler at pobox.com>]

On Wed, Apr 09, 2003 at 01:04:57PM +0200, Stephane Bortzmeyer wrote:
> > Diagnostic-Code: SMTP; 553 5.1.8 <sue at africaleaf.com>... Domain of sender
> > address sue at africaleaf.com does not exist
> 
> It is a bad idea to send a permanent error code (518) for a DNS
> problem, anyway, since they may be transitory.

Unless one of the nameservers is giving an authoritative "this domain does
not exist" answer, rather than a SERVFAIL.

africaleaf.com:

$ dig  at a.gtld-servers.net. africaleaf.com. mx
;; AUTHORITY SECTION:
africaleaf.com.         2D IN NS        ruo.leland-mw.org.
africaleaf.com.         2D IN NS        omega.eomw.net.
;; ADDITIONAL SECTION:
omega.eomw.net.         2D IN A         62.192.133.162

$ dig  at 62.192.133.162 africaleaf.com. mx
;; ANSWER SECTION:
africaleaf.com.         1D IN MX        10 omega.eomw.net.
;; AUTHORITY SECTION:
africaleaf.com.         1D IN NS        omega.eomw.net.
;; ADDITIONAL SECTION:
omega.eomw.net.         1D IN A         62.192.133.162

(The zone is missing an NS record, it should also have 'NS
ruo.leland-mw.org')

$ dig  at ruo.leland-mw.org. africaleaf.com. mx
;; res_nsend to server ruo.leland-mw.org.  62.192.133.1: Operation timed out

Hmm, try again:

$ dig  at ruo.leland-mw.org. africaleaf.com. mx
;; ANSWER SECTION:
africaleaf.com.         23h59m59s IN MX  10 omega.eomw.net.

;; AUTHORITY SECTION:
africaleaf.com.         23h59m59s IN NS  omega.eomw.net.

;; ADDITIONAL SECTION:
omega.eomw.net.         20h52m30s IN A  62.192.133.162

This is a 'lame delegation' - a delegation to a server which is not
authoritative for this domain, and is thus just acting as a cache. You can
see this by the way the TTL is counting down.

Definitely needs fixing. Either set it up as a secondary, or get yourself a
different secondary.

The same problem occurs for 'omega.eomw.net' - it has ruo.leland-mw.org
listed as an NS server within the zone, but it is not authoritative for
eomw.net.

There is an automated tool which does all this:
   http://www.squish.net/dnscheck
although it's very helpful to understand how to do the checking manually
using 'dig' first.

Cheers,

Brian.

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