A cloud-based identity and access management service for securing user authentication and resource access
You can create an alias, then you'll be able to use that alias for sign in anywhere you can sign in with your microsoft account.
https://support.microsoft.com/en-us/office/add-or-remove-an-email-alias-in-outlook-com-459b1989-356d-40fa-a689-8f285b13f1f2
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