Suppose you have the following A record:

example.com. 3599 IN A

And these MX records:

example.com. 997 IN MX 10 mx01.1and1.co.uk.example.
example.com. 997 IN MX 10 mx00.1and1.co.uk.example.

And you then changed the IP address for the A record to a non 1&1 ip address (so that the website could be hosted on an external hosting), would that affect the MX records or mess up the email in any way?

  • It does not affect the MX records. However, if your email client is set up to send or receive email via example.com, then making the change will disrupt your ability to send/receive email. You can work around this issue by setting up a new A record like host.example.com. 3599 IN A, and then reconfiguring your email client to send/receive email via host.example.com instead of example.com. – rinogo Feb 20 '20 at 21:00

No, email would not be affected.

The only situation where changing an A record would affect email was if you were changing an A record like mail.example.com which your MX records were pointing at.

  • Thanks, I think I understand. So if the target of the mx records (mx01.1and1.co.uk.) was actually (mail.example.com.) it would affect it, otherwise it wouldn't. Is that right? – Marc Mar 30 '18 at 12:10
  • Yes, that's correct.. – Tim Fountain Mar 30 '18 at 12:11

To add some more info here as an explainer for future visitors:

The A record tells the internet where to find the web site for a domain.

The MX record tell the internet which service is handling email.

A basic setup might be to have an A record

example.com. 3599 IN A 111.123.456.78

and then mail.example.com points to the same IP address with an A record

mail.example.com. 3599 IN A 111.123.456.78

or a CNAME record

mail.example.com. 3599 IN CNAME example.com

Then the MX record set up would be

example.com. 997 IN MX 10 mail.example.com

However, if the MX record was set up as Marc (the OP) has it

example.com. 997 IN MX 10 mx00.1and1.co.uk.

then the mail.example.com record would be redundant as the server managing DNS would not be handling email at all.

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