Email addresses and phone numbers associated with your Microsoft account are called aliases, and they use the same contacts, online storage, subscriptions, and account settings. Your aliases share a single password.
By default, all of your aliases can be used to sign in, but you can block sign-in for certain aliases. To restrict sign-in for certain aliases:
Sign in to your Microsoft personal account at account.microsoft.com and select Your info, then Sign-in preferences.
Choose which aliases are allowed to sign in to your account and select Save.
See also
How to fix "This username has been turned off" error
Add or remove an email alias in Outlook.com
How to help keep your Microsoft account safe and secure
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Important
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