We are having a problem with some ISP's like AOL the do reverse Looks ups on incoming email.
Basicly we have a mail server sitting behind a Watchguard Firewall. The Firewall is doing 1 to 1 NAT from the external IP address to the mail server.
The problem is the External IP adrress the mail is routed from appears to the the Gateway address and not the mail server address.
So if some one send me an email my MX record sends it to 22.214.171.124
However when I send out and email it comes from my Gateway of 126.96.36.199