I have a Barracuda Spam Firewall, and an Exchange 2000 Server behing a PIX Firewall. We have been experiencing issues with being blocked by SBC, so outgoing email is rejected.
Mail.ourdomain.com resolved to the Barracuda, but the Exchange Server has another IP. Because of this, reverse DNS is not working properly, and we believe this is why we get rejected. Outgoing email is forwarded back out the Barracuda.
The PIX is not able to forward the SMTP port on the Exchange IP to the Barracuda (outdated firmware which client does not want to pay to upgrade).
I have been struggling to come up with a solution for this. Does anyone know how I can fix this?