Question : Generic DNS denied

Hello,

1. Windows 2003 Standard Server, SP1
2. Exchange 2003 Standard Server, SP2
3. Using a POP3 pulldown program called PopCon to pull emails from our email host to our exchange server. Users then get their emails from exchange. When they reply the email go out through our Exchange server. Thus the problem lies there.
4. We have a static IP.

Could someone possibly display step by step how to do this or should I open a new question an offer points? Sorry if I am not following the rules here.
 

Error Message:

job-31775264133@craigslist.org on 4/24/2007 12:15 PM
            There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            01.pacbell.net[xx.xx.xx.xx]>: Client host rejected: Please use SMTP relay of your ISP or setup non-generic DNS>

Answer : Generic DNS denied

Ask your ISP to give you a reverse DNS entry on that IP address, and change your SMTP greeting from server.domain.local to yourserver.domain.com (this should be a real address, the same as the reverse DNS entry)

http://help.block.net.au/SMTP-Greeting.htm

-red