Email on, from what I believe is not having a reverse DNS

Posted on 2007-08-02
Last Modified: 2010-04-18
Hi Experts,

I just started picking up jobs for this client and looked into why their emails were getting denied.

Here is the SORBS record:

Netblock: (
Record Created:
Sun Oct 10 13:41:44 2004 GMT
Record Updated:
Sun Oct 10 13:41:44 2004 GMT
Additional Information:
Dynamic/Generic IP/rDNS address, use your ISPs mail server or get rDNS set to indicate static assignment.

I ran the site on and got this from the report...

This got a FAIL:

Reverse DNS entries for MX records      
ERROR: None of your mail server(s) seem to have reverse DNS (PTR) entries (I didn't get any responses for them). RFC1912 2.1 says you should have a reverse DNS for all your mail servers. It is strongly urged that you have them, as many mailservers will not accept mail from mailservers with no reverse DNS entry. You can double-check using the 'Reverse DNS Lookup' tool at the DNSstuff site (it contacts your servers in real time; the reverse DNS lookups in the DNS report use our local caching DNS server).

Its funny, that it was flagged by the day it was registered which i got from the whois.

I need to get a reverse DNS entry into their mailserver.

How do I do this? I have access to the exchange server or sbs.

Please let me know if I am missing anything.


Question by:JeramieD
    1 Comment
    LVL 74

    Accepted Solution

    Well, that's true that there is not a reverse DNS entry for the IP address (  That is provided by the Internet Access Provider that owns the IP.  But that won't help you with Sorbs... because as it says in the "Additional Information":
    Dynamic/Generic IP/rDNS address, use your ISPs mail server or get rDNS set to indicate static assignment

    Since is classified as being part of a Dynamic IP Address range you cannot send email directly from that IP.  So you need to configure a SmartHost to route email through your ISP's SMTP server.  This is done by rerunning the Configure Email and Internet Connection Wizard (CEICW -- linked as "Connect to the Internet on the To-Do list in the Server Management Console)

    A visual how-to for that is here:

    Check with the ISP to determine the appropriate Smart Host Name.


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