Reverse DNS

By stephen ·

We run SBS2003 and recently found we were unable to send emails to a particular customer, sending from an external private webmail account was successful. I turned Exchange logging up to a higher setting and found the following two errors for the problem emails: 7002 & 4007 both of which mentioned ?Possibly forged hostname for xx.xx.xx.xx? (our IP address).

Having spoken to our ISP they have no reverse DNS record setup for us, so I assume this is the answer to the problem. However I am not sure exactly what the reverse DNS record should say and unfortunately the tech desk at our ISP was not helpful at all.

I have done some comparisons of message headers from other small companies and compared to their nslookup results and for the most part see that their nslookup result matches the ?HELO=xxxxxx? text in their email message source. This seemed to work for 90% of the emails I checked.

So? am I right in thinking our reverse DNS record at our ISP needs to be the same as the message source text value against ?HELO=xxxxx? in the emails our server sends?

Thanks in advance!

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