Using New Outlook on Windows for professional communication and productivity
Hello,
You can change the alias for your Microsoft account, but you cannot use an existing outlook or hotmail.com address because they are already their own Microsoft accoutns, and Microsoft doesn't support merging Microsoft accounts.
Microsoft explains it here: https://support.microsoft.com/office/add-or-rem...
Go to Your Info > Sign in preference, Add an alias.
You have two options here:
Create new: this will allow you to use the native domain outlook.com to create a new alias.
Add existing: this will allow you to add a 3rd party email address, such as yahoo, gmail, as long as they are not already associated with another Microsoft account.