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Reverse DNS on multiple domains with one Internet connection

Posted on 2012-03-19
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Last Modified: 2012-04-02
I regularly use two different domains to send and receive mail in our organisation.

Example.com.au
Example.edu.au

I found that some clients often did receive our emails so I configured reverse DNS with Example.com with our ISP. As soon as I did that the issue was resolved.

I wanted to setup reverse DNS on our other domain Example.edu.au but our ISP said that we can only setup reverse DNS on one domain.

As a result, we purchased addition IP addresses for our internet connection and configured reverse DNS on another IP address that we have been allocated..

My question is;

Do I need to change the MX record on Example.edu.au to point to the IP address that we configured reverse DNS on? Or doesn’t it matter as it is on the same internet connection?
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Question by:the_omnific
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6 Comments
 
LVL 7

Expert Comment

by:lucifer82
ID: 37737044
If the Exchange that is hosting is using the same IP address it should be fine to leave it in the same MX record.
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LVL 9

Expert Comment

by:TazDevil1674
ID: 37737059
In the past, I have maintained an Exchange System thats utilised 6 Domains, we only every had a single IP for Exchange and used the primary domain name as part of the rDNS.

If you look at hosted exchange solutions - the rDNS on their system will be their own - none of the cusomters' domains will be mentioned.


A second Public IP wouldnt be important.
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LVL 30

Assisted Solution

by:Kerem ERSOY
Kerem ERSOY earned 500 total points
ID: 37737073
Hi,

First of all if we assume that you have 2 domains with MX set-up sucha as:

Exchange server address: exchange.example.edu.au your first domain examle edu.adu will be set-up such as:

In the DNS you will have the address of :
exchange.example.edu.au

You ned to have MX record as:
exchange.example.edu.au

In reverse DNS you will have:
IP and exchange.example.edu.au.

In example.com.au domain all you need is:

MX record that is pointing to exchange.example.edu.au.

This is it. So you don't need second IP and Second Reverse DNS.

You'll need different IP's, different reverse and forward DNS if and only if you want to name your mail server:

exchange.example.edu.au as your MX in your example.edu.au domain
exchange.example.com.au as your MX in your example.com.au domain.

If this is not the case only One IP and One Reverse Domain is enough. AS you would notice 2 separate Reverse DNS is only required if you have  2 different domains which defines your MX host as native to their domain..

Cheers,
K.
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LVL 1

Author Comment

by:the_omnific
ID: 37737081
The reason I ask is that some of our clients don't receive emails from our example.edu.au domain. It was exactly the same issue we had with example.com domain before we setup rDNS with our ISP. So I need to setup rDNS on our second domain. Just need to make sure I'm doing it correctly

Yes we use Microsoft exchange
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LVL 30

Accepted Solution

by:
Kerem ERSOY earned 500 total points
ID: 37737491
If you're having trouble getting mail for soma domain there can be multiple reasons..

First of all your MX host should have a Reverse DNS entry and all settings are OK:
http://www.intodns.com/

Then please check that your DNS has been setup for SPF:
http://www.intodns.com/
http://www.openspf.org/
http://www.kitterman.com/spf/validate.html


Lastly make sure that your IP is still reputable and not in any blacklists:
https://www.senderscore.org/
http://www.mxtoolbox.com/


Cheers,
K.
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LVL 5

Expert Comment

by:pradeep7880
ID: 37741138
Cannt you use a Alias in DNS? like CNAME?
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