Why does Office 365 need to confirm that I own my domain?
Before you set up Office 365 to use your custom domain name, we have to make sure that you own the domain. Otherwise, anyone could use any domain name they wanted to. For example, someone could use your domain name with Office 365 and say they were you!
The Office 365 domains setup wizard walks you through creating the verification record. Sign in to Office 365 to get started. You'll start the wizard, type in your domain name, (like fourthcoffee.com) and then the wizard walks you through the setup steps.
To prove that you own the domain, you create a DNS record with specific information in it (we provide the info in your Office 365 account) at your domain's registrar or DNS host. When you've done that, you tell Office 365 to look for that record. When Office 365 finds it, that confirms to the service that you own the domain. You must own it, because you had to sign in to the website where your domain is managed to create the verification record for your domain.
The record that you create doesn’t affect email or any other services. After Office 365 checks for the record and confirms that you own the domain, you can delete the record if you like.
If you're not sure where to go to add the record, you can learn how to find your domain's DNS host. The DNS records for your domain are usually managed by the same company where you bought the domain, especially if you haven't started using the domain for email or a website. But it might be managed by another company; for example, sometimes DNS management might be moved when you host a website with another company. If you’re not sure whether that happened, contact Support for the company that hosts your website.