How to force SMTP outbound from specific IP on ASA 5516?

[jesse wallace]

Running ASA ver 9.6.1

I have 5 public IP addresses. The first address in the bucket is assigned to my ASA. Our public ip for our mail server is the last IP in the bucket.

By default, outbound mail flows thru the IP of the ASA, which interferes w/RDNS.

I could change the IP of our mail server to the IP of the ASA, but that's a patch. I want to know how to force all outbound SMTP traffic to source from specific IP. It's a very straightforward principal, but I just can't figure out how to do it on the ASA.

Thanks so much in advance.

:)

[Aditya Ganjoo]

Hi Jesse,

You can either PAT the SMTP server to a specific public IP or use a static NAT so that it uses the same IP for the outbound traffic.

Regards,

Aditya

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