Mailing List Message #10128
From: Global Homes Webmaster <>
Subject: Re: resolving domains, with multiple domains on server?
Date: Thu, 31 Jan 2002 11:13:25 -0800
To: <>
X-Mailer: Mailsmith 1.1.8 (Bluto)
On 01/31/02 at 09:22, Brian Findlay wrote:

> I have been having some problems, related to our local ISP in town bouncing
> messages, and not delivering them, due to the 'from' domain (my server)'not
> resolving'.  This confuses me.  My DNS records with Network Solutions, are
> set up correctly, and the domains themselves serve just fine.  Performing a
> whois on any of these domains correctly points to my (single IP) server.
> The general settings main domian in SIMS is set to another domain (not
> mine), and if I switch it, the routre doesn't recognize any addresses
> anymore.

As your ISP sysop mentions below, whois is not the actual DNS data. It just
gives human-readable information about domain name registrations.

> Here is a snip from the sysop at the ISP, telling me what the problem is...
> **** bounced message clip ****
> .... while talking to
> >>> MAIL From:<> SIZE=565
> <<< 451 4.1.8 <>... Domain of sender
> address does not resolve
> <>... Deferred: 451 4.1.8
> <>... Domain of sender address
> does not resolve
> Warning: message still undelivered after 4 hours
> Will keep trying until message is 3 days old
> ****** end *****
> ***** ISP sysop reply to my inquiry *****
> Here is what I get when I look you up: (more below)
> --------------------------------------------------------------------
> "sun:/work/users/akoppel# nslookup
> Server:
> Address:
> Non-authoritative answer:
> Name:
> Address:
> nslookup
> Server:
> Address:
> *** can't find Non-existent host/domain
> sun:/work/users/akoppel#
> ----------------------------------------------------------------------------
> That means that I can translate to an address

He can look up in DNS and resolve it to an IP address

> when mail comes from, I do not know who the heck you are,
> so I do not trust you, so I will not handle your mail.

When he does a DNS look-up of the address, he can't resolve it
back to a domain name (i.e. the host name of the machine at that address).
When I do the look-up, I do get an answer, but it's the wrong record type -- a
CNAME that points nowhere. I'm not really sure what this guy thinks this has
to do with your problem, though -- the bounce message cites an error in
resolving the sender's domain name, not the IP address of the sending server.
At any rate, it sounds like his mail server won't accept messages from senders
that don't have valid reverse DNS. Whether or not that's a good thing is

> Talk to the name of the person who handles your DNS resolution.. and have
> him check/update his REVERSE DNS table (  as well as table.ptr).

He wants you to add a record to the reverse DNS for your mail server's IP
address so that will resolve to a domain name (preferably the
same name that you've got as SIMS' 'Internet domain name' in the general
settings). Something like:   PTR

> If you share this message with you provider, he should know what I mean.

Didn't you say this guy works for your ISP? If so, isn't he the person that
he's suggesting you talk to?

> This is independent of your Whois entries.
> *****  end   *****
> So what does all this mean??  What is a 'REVERSE DNS' table, and where is
> it, and how do I update it??  I manage the DNS server for this site
> (MacDNS), and I looked for such a setting, but could see nothing that seemed
> close.

One of MacDNS' many failings is that it does not do reverse DNS. You should
talk to whoever is responsible for your reverse DNS (probably your ISP --
looks like and get them to add appropriate records for the IP
addresses that you use. From my look-up of your IP address, it appears that
the reverse DNS is screwed up to begin with, so it needs to be fixed in any

                   Christopher Bort |
            Webmaster, Global Homes |
      <> | PGP public key available on request
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