How to change the DNS of a domain already in use

Knowledgebase

Changing the DNS of a domain that already works takes more care than setting up a new one. Here you are not starting from nothing: there is a live site and e-mail arriving, and a careless change interrupts both.

Before changing anything, record the current setup. When you switch nameservers, the whole previous zone stops applying — and nobody hands it back to you. Screenshot every record: A, CNAME, MX and TXT.

First decide what you actually need to change

Goal	What to change	Risk
Move the site to another server, keep everything else	Only the A record	Low
Move only e-mail to another provider	Only the MX records	Low
Hand all DNS management to another provider	The nameservers	High

If you only need to change where the site points, leave the nameservers alone. Changing just the A record is faster, propagates sooner and puts no e-mail at risk.

Lower the TTL a few days ahead

The TTL tells other servers how long to keep an answer before asking again. If it is high, your change takes a long time to reach everyone.

Lower the TTL on the records you are about to change to something short — 300 seconds, say — and wait at least a day. Then, when you make the real change, it propagates in minutes instead of hours. Once the move is done, set it back to normal.

Making the change

Where you do it depends on who manages the DNS right now — not on who hosts the site:

If the domain uses...	Change it in
Our nameservers (dns1-4.mozout.com)	cPanel → Zone Editor, or My MozOut → DNS Manager
Another provider’s nameservers	That provider’s panel
You are switching the nameservers themselves	Where the domain is registered

Edit records in the wrong place and nothing happens — not even an error. You simply wait for a change that never arrives.

If you really are switching nameservers

In that case the old zone disappears. After switching, you must recreate every record in the new service before things return to normal:

• The domain’s A record and the www one

• The MX records — miss these and e-mail stops immediately

• The SPF and DKIM TXT records, or your mail starts landing in recipients’ spam

• Any subdomains that pointed at other services

Confirming it worked

Do not rely on your own computer — the browser holds on to the old answer for a while. Check from several countries, as explained in how to check a domain’s DNS. While some locations show the new value and others the old, it is still propagating.

With a live site at stake, it is worth checking first. Tell us what you plan to change.

Open a support ticket