Moving DNS management from Office 365 to my own host

I think you are confusing the roles of a registrar and nameserver, and yes they can be the same.

The registrar, is the company that you purchase a domain, register it with ICANN, and manages your NS, DS, and Glue records with upstream nameservers.

Many registrars offer nameservers as an included service.

Your nameservers simply answer dns requests. These are the two providers you mention.

If you are looking to switch to Google apps, I'd highly recommend transferring your domain to Google domains, it's an excellent service and not bad on the bank, in the process they will attempt to transfer your zone from Microsoft. This zone file is never complete, you should always backup and transfer the data in your zone file first.

Also, Google apps actually allows you to deliver email to both gsuite, office 365, and any number of additional destinations with their dual delivery. this way you can update your mx records before migrating users and make migration easier.

Good Luck

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