SMTP route to Email Public address

[galin.gospodinov]

Hello community, 

i have a question, but can`t find answer on it. 

If we have one listener for inbound and outbound communication and this private IP has NAT to public IP. We don`t have communication to mail server on private IP.  Is it a problem if we use mail server public IP address ? This public IP is configured on SMTP routes and RAT. 

The NAT public IP of ESA and MAIL server are on same pool.

What may be the issues in this scenario ?

[Ken Stieers]

Depends upon if your firewall lets you hairpin traffic. Often it won't let something inside connect to the external IPs.
There isn't a "problem" per se, but in this case I wonder why you have the email server exposed now that you can expose the ESA, a hardened security device, instead.




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[galin.gospodinov]

The email server administrator has some concerns and don`t want to create separate interface for private communication between mail server and ESA. The only option to convince him, that this is not the right topology,  is to tell him more disadvantages. 

[Ken Stieers]

"Just won't work through firewall" is a pretty good reason.
Exposing email server to internet needlessly, also a good one.
Your "outbound" interface IS the "interface for private communication between the email server and ESA"


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This email is intended solely for the use of the individual to whom it is addressed and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If the reader of this email is not the intended recipient or the employee or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited.
If you have received this communication in error, please immediately notify us by telephone and return the original message to us at the listed email address.
Thank You.