mail server DNS configuration questions

Kevin Kinsey kdk at
Sun Sep 7 20:14:49 UTC 2008

Andrew Falanga wrote:

>> *Not having* a reverse entry for a mail server is often
>> the cause of issues.
> This I do know very well.  I had similar problems when running a sendmail 
> backup spooler for Syracuse Networks back in 2000.  The eventual solution was 
> that our ISP delegated control of our subnet to us.  I'm wondering if 
> something similar must be done on the internal network, i.e.  
> Perhaps I shouldn't have eluded to the problems that my clients are 
> experiencing.  The real question is, should I configure a sub-domain under 
> for this server and if so, how to set it up?
> I'm interested as to why you got this answer to the host query you did.  In my 
> original mail, I provided the result of a reverse lookup on that IP address 
> to which I got this response:
> [/usr/home/andy]
> -> dig +short -x
> Using host, on my machine, I get this response:
> [/usr/home/andy]
> -> host
> domain name pointer

Well, interestingly enough:

[30] Sun 07.Sep.2008 DING!
[kadmin at archangel][~/logs]
host domain name pointer

So something's changed in the last 12 hours, although I can't
say exactly what.  AFAIK, my DNS boxen and I were communicating
Just Fine(tm) last night as well as this afternoon.
> Regardless of the fact that I got a response and you didn't, I'm still not 
> getting the right information.  The reverse mapping should be something like:
> I may have gotten the syntax wrong as it's been a while since I've had to 
> manipulate BIND name tables.
>> And the RFC for ESMTP is #2821.
> Thanks for the RFC.
> Andy

Well, at this point, I'd take the day off, and tomorrow
perhaps have a "dig" at cableone's support ppl, looky here:

[35] Sun 07.Sep.2008 14:03:43
[kadmin at archangel][~/logs]

; <<>> DiG 9.4.2-P1 <<>>
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 56668
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;                    IN      A

.                       3600    IN      SOA     A.ROOT-SERVERS.NET. NSTLD.VERISIGN-GRS.COM. 
2008090700 1800 900 604800 86400

;; Query time: 222 msec
;; WHEN: Sun Sep  7 14:03:50 2008
;; MSG SIZE  rcvd: 103

So, it's obvious they're playing with this zone Right Now(tm),
(more or less) as the SN seems to indicate today.  Possible this
is auto-generated or something, but I think you'll get no joy
on the PTR records until they do something upstream.  As for
your internal net, I don't know much about it, unfortunately.


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