I am transitioning ffrom an Exchange 2000 server to an Exchange 2007 server. Mail sent from mailboxes on the existing 2000 server pass reverse DNS looklups but mail sent from the new 2007 server fails. We use TrendMicro IMHS for our spam filtering, so our MX record is pointed at Trend. Trend Says that they are not providing reverse lookup info and I need to request it from my ISP. My ISP is Network Solutions. when I look at my DNS entries on the Network Solutions website I do not see an option for reverse lookup. I have (A) records set up for the public addresses of both servers. Most mail domains are rejecting mail from my new server . I am testing with an sbcglobal.net account that accepts mail from my new server, but, it says right in the headre that it failed reverse lookup. Can anyone help?