ASA and email server NAT / PAT question


We own a block of IPs. Our ASA currently is using IP1.  We also had an Exchange 2003 ( server that had no NAT and was using IP1 to get out.  I recently upgrade to Exchange 2010 ( to a new hardware and created a NAT for IP2 for OWA (https) purposes.

All inbound SMTP traffic is being sent to a Barracuda ( 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 - 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 is configured, will tcp smtp from server go out as IP1?

Thanks in advance.

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Ken BooneNetwork ConsultantCommented:
Since you did a NAT for IP2 all traffic going in and out of the ASA will be using the NAT address of IP2.  So if remove the NAT and do a PAT on tcp 443 for IP2 then smtp traffic will go out as the IP address of the ASA.

So OWA will still work on IP2 but outbound SMTP will use IP1.

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Pro4iaAuthor Commented:
great.  replaced static NAT with a PAT and all is good. thanks.
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