We help IT Professionals succeed at work.

We've partnered with Certified Experts, Carl Webster and Richard Faulkner, to bring you two Citrix podcasts. Learn about 2020 trends and get answers to your biggest Citrix questions!Listen Now


Outgoing SMTP connection using different IP that incoming IP. Causing reverse DNS issues

Medium Priority
Last Modified: 2012-05-06
I am currently running a 2003 Exchange Standard server. Router IP is incoming smtp is Reverse DNS is setup correctly to yet when the server makes an outgoing connection it is coming from and being denied for rDNS due to the incorrect IP. How do I make Exchange use the correct outgoing IP for this to work correctly? Or do I have to change my NAT to move the Exchange server to the Routers IP?
Watch Question

Why do you say that Reverse DNS is setup correctly to when is should be based on the router IP, not incoming smtp?

Not the solution you were looking for? Getting a personalized solution is easy.

Ask the Experts
So the reverse dns should point to the router and not the IP used for the mail server? Crap!

What do you have in front of the Exchange server? When you go to whatismyip.com from the Exchange server, what do you get as an IP address? If it is something other than, then you have a routing problem with your firewall/router.

Reverse DNS should be pointing to whatever is the external IP address of the Exchange server.
Access more of Experts Exchange with a free account
Thanks for using Experts Exchange.

Create a free account to continue.

Limited access with a free account allows you to:

  • View three pieces of content (articles, solutions, posts, and videos)
  • Ask the experts questions (counted toward content limit)
  • Customize your dashboard and profile

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.


Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.