We just purchased a Barracuda SPAM Filter to replace our old eSOFT Spam Filter appliance. The SPAM Filter inspects messages and forwards them to our internal Exchange Server. The SPAM FIlter sites on our LAN along with our Exchange Server, and both sit behind our Corporate Firewall.
Needless to say, every since I switched to the Barracuda, our email's are getting rejected by some Domains. For example, we can't send to "Comcast.net". In our SMTP log on our Exchange server, I see an error regarding an invalid Reverse PTR record. Our ISP hosts our DNS for our mail server, and I had them switch the hostname to resolve to the hostname of our Barracuda SPAM filter. However, I still can't sent to comcast. The emails are sitting in our Exchange server queue for up to 24 hours, and eventually we receive an NDR.
Finally, according to some of the free DNS online tools, my MX record seems to resolve properly. Any suggestions?