Reverse DNS

Posted on 2011-02-24
Last Modified: 2012-05-11
We have 3 main sites each with there own Exchange 2010 server, MX records are pointing to one site which collects mail for multiple domains (different sub companies) and then distributes them to the corresponding mailboxes, this was found to be the best setup as users from the sub companies are spread across different sites..
Each site though sends out using it's own exchange server, the problem we are getting is with reverse DNS which resolves to the one site so we are getting bounce backs from certain mailservers as the rDNS does not correspond with the sending site.
The way I see it is that I can't have one A record pointing to different ip's as when I enter this as an MX record mail will be sent to both, great for load balancing but not for our set up were we only want one server to receive external mail. how would I go about setting up multiple ip's for a single MX record?
Question by:carn
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Expert Comment

ID: 34969168

Accepted Solution

Saineolai earned 125 total points
ID: 34969191
The reverse dns lookup should be for the fully qualified domain name of the sending Exchange server's smtp service.

Ensure that reverse lookup for each IP address matches the fully qualified domain name on each server.

Author Comment

ID: 34969323
Thanks saineolai don't know why I was thinking it had to match the MX? when you say FQDN are we talking internal or external ie. when I telnet to our mail server on port 25 it responds with it's internal domain name.
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Expert Comment

ID: 34969345
It should be dns name that it responds with when you telnet to it from the outside of your network.

This should be an external domain name, although if not configured in the Exchange configuration it will use the internal one.

Expert Comment

ID: 34969354
Have a look under FQDN on this page:


Author Comment

ID: 34969362
would there be any problems with using the internal (which is what it responds with externally)

Expert Comment

ID: 34969422
You ISP will not create a reverse dns entry for a private dns zone (.i.e., company.local).  If the internal dns zone is a valid domain e.g. .net, .com .org then there should be no problem.

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