How to buy a domain name
If you don’t already have your own domain, you can easily buy one online, for example from a domain registrar or a domain reseller. You get a domain name when you sign up for Office 365, for example, contoso.onmicrosoft.com. But you may want to use a custom domain name, like fourthcoffee.com.
To set up a domain in Office 365, you must own a domain and change some of the DNS records for your domain.
Caution Some domain registrars or DNS hosting providers don’t allow creating all the DNS records required by Office 365. Registrars listed here support all the needed records. If you’re thinking of using a different registrar, learn about potential service limitations.
After you register your domain (at a domain registrar), you sign in to Office 365 as an admin and set up your domain so you can use it with your email address and other services.
Buy a domain from Go Daddy
You can buy a domain from Go Daddy directly from Office 365 when you’re signed in to the portal.
Additional domain registrars that support all DNS records required for Office 365
To buy a domain from a domain registrar other than Go Daddy, it’s best to choose one that supports all DNS records needed by Office 365 services, such as the following.
Transfer your domain to a different domain name registrar
If your domain is registered at a provider that doesn’t support all the necessary DNS records, you can transfer it to a different provider. When you transfer the domain, you change who you send payments to in order to renew and keep your domain name.
Request the transfer at the registrar that you want to move your domain to. Look on their website for an option such as Transfer DNS. After they make the changes, it can take a few days update across the internet.