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Old 02-10-2016, 01:09 PM   #1
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CNAMEs and MX Records

Hi. I've got this situation where we have a Web site and an email service hosted by a friend of our business, but the domain and DNS is under control of our registrar. Basically, the DNS right now is just a CNAME pointing to one of their domain names. There is no MX record entries on our side, so evidently DNS lookups just use the MX records for their domain. (Testing with dig confirms this.)

I want to leave the Web hosting as is, but transfer the email hosting to our email server. My question: If I just define an MX record, but leave the CNAME as it is, will our MX records "override" theirs and do what I want? Or do I need to replace the CNAME record with an AA record?
Old 02-10-2016, 01:36 PM   #2
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Its a bit muddy.

I'm assuming you're saying you have something like has records (e.g. "A" or "AAAA" pointing to a specific IP for their web service. has CNAME records pointing to (and maybe has CNAME to or

If so those records say where the main domain goes.

The "MX" is a separate record type. You typically defined that as a name like then have a separate record (usually an "A" or "AAAA") that defines mailserver in the zone file as a specific IP (which may or may not be the same as the one you're using in base setup for web service as well). It might be a CNAME itself but I've not done CNAMEs for these. The important thing here is you have two separate records. One is the MX that tells people what mail server name to use and another that tells people where to find that mail server name (e.g. by its IP).

Usually if you're using the Registrar's DNS setup they have place where you can update records for First you'd want to see if you have an MX record for their. If so you'd change that entry to point to your mailserver name. If your mailserver name is not in the the Registrar's DNS setup for then you'd also have to add that record.

How you do that at the Registrar depends on who the Registrar is but the concept is the same.

Last edited by MensaWater; 02-10-2016 at 04:05 PM.


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