I run my own email server (postfix) and my own DNS servers (bind) on openSUSE 11.2. Lately I've found that I cannot send email to Comcast users, apparently because they cannot do a reverse DNS on my IP address. I do have PTR records set up correctly as far as I know.

I can do a reverse lookup from my local machine with no problem but if I try from outside my network it says the IP address doesn't exist. Is there something else I need to do besides setting up my PTR records to get this to work?

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  • Does the E-Mail server have a fixed or dynamic IP address? – Pekka 웃 Dec 21 '09 at 2:43

Reverse DNS entries have to be handled by your service provider. Most hosting companies will handle this in minutes via a helpdesk ticket or other support interface.


Try with this website and see what it comes back with..

Some companies are starting to do Forward confirmed Reverse DNS which started causing and issue because my emails were going out through a firewall, so the recieving end saw the email coming from a different ip address than my email server. so even when my smtp banner was resolving to the email server ip address and the domain where the email came from resolved to the same ip address, they were also FCrDNS the ip address were my email came from and it wasnt matching the ip address of the server.

Info on FCrDNS

You can also make sure that your domain has the right SPF records set up.


Yes, I do have the same problem like the following:

Diagnostic information for administrators:

Generating server: mail.domain.com

mail.abacusevents.com # #SMTP# 

which records should I add into my internal DNS or my ISP DNS server ? MX or PTR for this problem ?

  • 1
    Probably you have already MX record, you should add PTR record. – vitalie Nov 24 '10 at 6:36
  • Yes i do have MX records, so in this case the PTR should contain the mailserver.domain.com ? – Senior Systems Engineer Dec 8 '10 at 2:12

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