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DNS splitting: How to do it exactly?

Sumukha used Ask the Experts™

I need to have a webserver hosted at a completely different server hosting company than the email server.

How can I exactly do this (step by step)?


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Hi Sumukha,

That is pretty straight forward.

You need an A record for each server.

one for "www" that points at the hosting company
one for "mail" that points at the mail server

Then you need an MX record, pointing to mail.domain.com

Finally, you will need a PTR record for your mail server

Are you trying to configure this yourself?  If so, with what DNS server?

Hope that helps,



Hi red,

That was fast...

I will probably have to do it myself, logging into the contol panel of the registrar which seems to be easydns.com.

The email is currently on one server, I need to set up the web server somewhere else. without any interruption for the mailserver.
I hope there will be no time out for the email server when the DNS is changed?
If all you are doing is moving www, then it should be relatively simple.

Just change the IP address of the alias for WWW (it should be obivous)

While it should be relatively quick, as you are only modifying a record, I wouldn't be taking the old server offline for at least 48 hours

Right now, what is your mx record?  Does it point to mydomain.com or www.mydomain.com (replace mydomain.com with your actual domain name)?  If so, BEFORE moving the web server, you should set up an A record for mail.mydomain.com to point to your mail server, and then point your MX record there.  You then need to wait for the information to propagate.  Then, move the A record for www.mydomain.com (and presumably, mydomain.com, if you want that to resolve for your website).  The MX record (which indicates the mail server) will then be entirely independent of the A recores for www.mydomain.com and mydomain.com - it will point to whatever mail.mydomain.com is, and there will be no problem.
beware your email will be down for a bit while DNS replicates... so make sure you access the old email server after 48 hours or so to see if there are any  emails missed and delivered to the old mailbox.
Expanding on what periwinkle said. If your MX is set to www.mydomain.com, add the new A record for mail.mydomain.com and create an additional MX record for it. Set that new MX record to a higher priority (i.e. lower numbered preference).

Basically the MX portion of your DNS will be something like this:

mydomain.com.             IN       MX       10          www.mydomain.com.
mydomain.com.             IN       MX        5           mail.mydomain.com.

This will ensure that mail will continue to be delivered no matter what. After 72 hours, you can remove the MX record for www.mydomain.com. At that point, you can make the change to the A record for www.mydomain.com at any time. Do note that there will be a period of 24-72 hours where some people will not be able to view the website due to DNS caching and propagation.