Correct MX setup for multiple domains hosted on the same exchange server.

Posted on 2007-10-08
Medium Priority
Last Modified: 2008-01-09
Hi guys,

In regards to hosting multiple domains on one exchange server.

If we setup a primary domain called webmail.example.com and setup reverse dns to webmail.example.com.

Should all other domains be setup with mx as webmail.example.com that way reverse dns will work on all domains?
ie. domain = example2.com mx = example.com
     domain = example3.com mx = example.com

or should we be using an A record mail.example1.com setup and then using that as the mx record mail.example1.com
ie. domain = example1.com mx = mail.example1.com
     domain = example2.com mx = mail.example2.com

I realise both methods would work but just wondering which would be the prefered method and which would give us better luck not being filtered as a spam site
Cheers for a heads up!
Question by:mishramanuj
LVL 39

Accepted Solution

redseatechnologies earned 200 total points
ID: 20038411
Flip a coin, it matters that much.

Will your customers care if people who can sniff DNS records know that you are hosting their mail?
LVL 13

Assisted Solution

bluetab earned 200 total points
ID: 20038804
It doesn't matter what your rDNS record shows.  The rDNS record doesn't have to match the MX record.  The purpose of the rDNS record is basically just to show "ownership" of the IP and that there is some sort of record setup on it.

Author Comment

ID: 20038806
Haha thats how we viewed it but I was a tad unsure how spam guards sniff DNS. ie if reverse dns reports a different address to the mx record it may decide its a borked email server address
LVL 71

Assisted Solution

by:Chris Dent
Chris Dent earned 100 total points
ID: 20039342

Blue is right, it doesn't have to match the MX.

The PTR Record must match up with the name the SMTP Server is sending out as.

That is, if the server is configured to send out as mail.example1.com, the PTR Record must match the IP the server uses to send to mail.example1.com.


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