Received the following error from a user:
WARNING: Forward-DNS does NOT match Reverse-DNS. DNS is INCONSISTENT.

Some users are having their email marked as spam. I looked in the PTR records and found the following information:
70.63.x.34 PTR - mail.x.com
70.63.x.36 PTR - mail.x.com

A record - mail.x.com -> 70.63.x.36

I guess my question would be; Should I remove the PTR from 70.63.x.34?

  • Doing a dig -t mx x.com. shows that the mx record points to mail.x.com – evolvd May 24 '11 at 16:27
  • but from which ip are you sending from? – David Schmitt May 24 '11 at 16:31
  • I looked at a header from a email that a client sent me and it shows that it is coming from 70.63.x.36 – evolvd May 24 '11 at 18:02

Yes, If you have no A record for mail.x.com set to 70.63.x.34. The recipient's email system likely has a spam filter that does reverse lookups on the sender's domain to help mark spam.


You haven't said how the mail server is actually configured to send mail which is the key bit.

Having an extra PTR record is not a problem. Sending mail from that IP is.

Try this:

dig -t mx x.com.
  • mx points to mail.x.com – evolvd May 24 '11 at 16:27
  • Then your .34 IP is not an issue. – dmourati May 24 '11 at 18:17

If you send mail from .36 you shouldn't have a problem. If you send from .34 you will have a problem, or if you send from both, you need both addresses as A records and both as PTR records and maybe as SPF records too!


Also, what is your server configured to say for the EHLO command? If you are reporting your internal server, it will not match.

In Exchange 2007/2010, you would go to Organization Configuration>Hub Transport>Send Connectors and on the General Tab in the "Specify the FQND this connector will provide in response to HELO or EHLO" field, enter that mail.x.com.

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