Comcast rejects mail from servers with no PTR record

Comcast rejects mail from servers with no PTR record

One of my clients got dozens of delivery failure messages. Here is a relevant snippet.  What needs to be done to add a PTR record to the mail server? Or do I need to configure something else?

----- Transcript of session follows ----- 
... while talking to mx2.comcast.net.: 
<<< 554 imta13.emeryville.ca.mail.comcast.net comcast 2600:3c01::f03c:91ff:fedf:ef66 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://postmaster.comcast.net/smtp-error-codes.php#554