moving to a Office 365 account from existing personal

Microsoft 365 Personal and Microsoft 365 Business are separate account types. There is no supported way to convert a personal Microsoft account into a Microsoft 365 business work account.

To set up domain email with Microsoft 365 Business:

1. Create a Microsoft 365 business tenant and business subscription.
   • The initial account is created with a default tenantname.onmicrosoft.com address.
   • That default domain is expected and is used as the starting admin account.
2. Add the custom domain to the business subscription.
   • In Microsoft 365, add the domain and complete the required DNS record updates so mail can route to Microsoft 365.
   • To add, modify, or remove domains, the required role is Domain Name Administrator.
3. Change the business admin/user email to the custom domain address after the domain is verified.
   • The onmicrosoft.com address can remain as the default routing domain, while the sign-in and email address can use the custom domain.
4. Move existing data separately.
   • Outlook email, calendar, and contacts can be exported from the old account to a .pst file in Outlook using File > Open & Export > Import/Export > Export to a File.
   • Then import that .pst into the new Microsoft 365 business account using File > Open & Export > Import/Export > Import from another program or file.

If only a few mailboxes are involved, mailbox owners can migrate their own email and contacts. If several mailboxes are involved, Exchange migration methods are available.

References:

• Trying to migrate to Microsoft 365: You can't sign in here with a personal account. Use your work or school account instead. - Microsoft Q&A
• Set up Microsoft 365 Business Standard with a new or existing domain
• Activate and set up Microsoft 365 Business Basic
• Plan your setup of Microsoft 365 for business