On Sun, 06 Jun 1999 03:03:20 EDT, "Alan S. Dobkin" <[log in to unmask]>  said:
> Error-Text: Mailer mxnx.berlinetz.de said:
> "550 '<[log in to unmask]>SIZE=35126'
> sender address target 'LISTSERV.CC.EMORY.EDU' is not a valid e-mail
> domain (there is no MX record for it)."

Aha.  *This* wonderful flake of the DNS again.

What probably happened is that the nameserfer on berlinetz.de
got back a DNS reply with an empty 'Answer' section (which
usually indicates a referral to the nameserver identified
in the 'authority' and 'additional' sections of the reply).
However, either the 'Authoritative Answer' bit was also
set (which implies the hostname is valid, but no MX or A
record was returned in the Answer section), or the client
resolver had the 'dont recurse' bit set.

The most likely culprit is the following:  'dig' reports
this information on listserv.cc.emory.edu:

;; ANSWERS:
listserv.cc.emory.edu.  86334   A       170.140.132.49

;; AUTHORITY RECORDS:
cc.EMORY.edu.   86334   NS      ns2.EMORY.edu.
cc.EMORY.edu.   86334   NS      AUTH02.NS.UU.NET.
cc.EMORY.edu.   86334   NS      NWS-Test3.cc.EMORY.edu.
cc.EMORY.edu.   86334   NS      ns1.EMORY.edu.

;; ADDITIONAL RECORDS:
ns2.EMORY.edu.  82014   A       170.140.2.1
AUTH02.NS.UU.NET.       157002  A       198.6.1.82
ns1.EMORY.edu.  86334   A       170.140.1.1

It's interesting that there's 4 entries in the Authority
area, but only 3 A records in the Additional section.
It could very well be that the berlinetz.de host chose
nws-test3 as the host to recurse to, was forced to do
another lookup to resolve THAT address, and got a timeout
or other error.

Lo and behold, there isn't an A record in the DNS for
nws-test3.cc.emory.edu.  Have your DNS jockeys either
remove it from the NS list, or add an A record for it.
Otherwise, an average of 25% of all off-campus lookups
of your addresses will at best have to wait for a timeout
and try one of the other 3 NS entries, or at worse
will error out entirely.

I've CC;ed them on this note.

                                Valdis Kletnieks
                                Computer Systems Senior Engineer
                                Virginia Tech