Reverse DNS

  • From: "Clay Niemann" <clayn@xxxxxxx>
  • To: "'[ExchangeList]'" <exchangelist@xxxxxxxxxxxxx>
  • Date: Tue, 31 Aug 2004 14:14:10 -0500

Hi. My company recently implemented an Exchange 2003 server. Most messages
are sent and received fine. However, some messages to larger providers like
AOL and Yahoo get delayed for a couple of days then fail altogether. I have
verified that I am not on a SPAM blacklist.

After looking around on Google I suspect the issue is related to reverse
DNS. The domain name that supports our LAN is fake (it isn't registered). We
do have a separate domain name for email that is registered. DNS hosted by
our ISP points the real domain to our Exchange server. They also configured
reverse DNS. We have an internal DNS server for hosts within our LAN.

I have a couple of hints that could indicate what is going on. First, when I
run nslookup on my Exchange server's public IP address is resolves as "mail" is not the host name of my mail server. Should I
have my ISP correct this in DNS? Should I add a PTR in my internal reverse
DNS for "mail" that points to the mail server?

The second hint is in the delay and failure messages. A text attachment is
sent with the delay message (with identifying info removed):

Reporting-MTA: dns;

Final-Recipient: rfc822;user@xxxxxxx
Action: delayed
Status: 4.4.7
Will-Retry-Until: Sun, 22 Aug 2004 09:36:23 -0500
X-Display-Name: user@xxxxxxx

Note that the Reporting-MTA: is pointing to the unregistered domain. This
line of text is in the failure message:

    Could not deliver the message in the time limit specified.  Please retry
or contact your administrator.
    < #4.4.7>

Again the message referes to the fake domain. Google says #4.4.7 just means
the message timed out.

I'm sure this is easy one for you guys, but I am new to Exchange and DNS.
Anys suggestions are greatly appreciated. 

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