I have had some issues sending email with the static IP assigned by my ISP, and I am considering forwarding all my outgoing mail to an external host, which will also filter the mail. However, I've been advised this system will insist on a valid reverse DNS lookup to accept email from our GroupWise system.

An example of one of the failed outgoing emails is the response here:
"Response: 554 cm7nec mx.talktalk.net axcCe5qYx52DX No PTR Record (TT105)"

How do I ensure that a correct PTR / Reverse DNS exists? Is it simply a matter of having the GWIA Hostname/DNS "A Record" name being fully correct / accurate?

Thanks in advance for any feedback