Currently, I have a static mapping of my public mail ip address to my Exchange server on the inside of the ASA 5510 using the statement below:
access-list outside extended permit tcp any host 69.3.216.x eq smtp
static (inside, outside) 69.3.216.x 192.168.1.x netmask 255.255.255.254
I added a mail-filtering gateway(Symantec Brightmail) into the configuration. On the mail gateway, I use two NICs; one for incoming mail and one for outgoing mail. I have modified the above mapping to point to the incoming NIC on the mail gateway as below:
static (inside, outside) 69.3.216.x 192.168.1.8 netmask 255.255.255.254
Once the incoming mails are filtered, they will be relayed to my Exchange server.
I have configured my Exchange server to relay outgoing mail to the gateway outoging NIC (192.168.1.9). The outgoing mail reach the mail gateway, but I don't know how to configure the ASA to map the outgoing NIC of the mail gateway (192.168.1.9) to my public mail ip address (69.3.216.x).
Can anyone help?