We own a block of IPs. Our ASA currently is using IP1. We also had an Exchange 2003 (10.1.1.10) server that had no NAT and was using IP1 to get out. I recently upgrade to Exchange 2010 (10.1.1.20) to a new hardware and created a NAT for IP2 for OWA (https) purposes.
All inbound SMTP traffic is being sent to a Barracuda (10.1.1.250) that's on our network then fwded to our e-mail server.
On the new server, I noticed a problem sending emails to a certain domain - for example abc.com - which we did not have before with our Exchange 2003. Recently I found out only IP1 was safelisted on this target domain. Unfortunately, safelisting IP2 involves a lot of work.
My question is (on the ASA) Instead of a static NAT, if a PAT on tcp https for IP1 and 10.1.1.20 is configured, will tcp smtp from 10.1.1.20 server go out as IP1?
Thanks in advance.