My (different) microsoft account doesn't recognize my email adress.

The “Added as an alias” email means that address was attached to an existing Microsoft account rather than necessarily creating a separate account, so try another alias or phone number belonging to that same account and then use Microsoft’s dedicated username has stopped working support route.

1. Try another sign-in name for the same account

An alias is an additional email address or phone number attached to one Microsoft account. All aliases share the same password, contacts, storage, subscriptions, and settings. An alias can also be disabled for sign-in while remaining associated with the account.^1^

If that account ever had another:

• Outlook, Hotmail, or Live address
• Non-Microsoft address, such as Gmail
• Phone number
• Skype name

try signing in with it and the same password. Microsoft specifically recommends another alias or phone number when the expected email is not recognized.^2^

If one works:

1. Open Your info.
2. Select Sign-in preferences.
3. Check whether the missing address remains listed under the account aliases.
4. Check whether it is allowed to sign in, then select Save.^1^

Do not remove an alias while investigating the problem.

The screenshot only establishes that the address was added at the time of that notification. It does not establish that it remains attached now, that it was enabled for sign-in, or that it was a separate Microsoft account.

2. Use the “username has stopped working” escalation

Since the ordinary recovery attempt was unsuccessful, use Microsoft’s page specifically for a previously working username:

1. Open My username and password have stopped working.
2. Expand If you still see “We couldn't find an account with that username.”
3. Select its Contact support button.
4. Tell the advocate:
   “This username previously worked and Microsoft sent an email confirming it was added as an alias, but it now says the account does not exist.”
5. Attach the screenshot privately and provide any other aliases or phone numbers previously associated with the account.

That is the documented assisted-support route for this exact message.^2^

3. If the website does not offer chat

On a Windows PC, open the Get Help app while signed in with this working Microsoft account:

1. Search for Microsoft account username stopped working.
2. Select Contact Support when offered.
3. Choose the affected product or service and select Confirm.
4. Choose Chat with a support agent in your web browser or request a callback, if available.

Contact options vary by product, scenario, subscription, and operating hours.^3^

Microsoft’s general support page can also route account and billing problems to an appropriate option, which may include chat.^4^

Important limitations

• Support agents cannot directly change account details or send password-reset links; account ownership must still be established.^4^
• If the account had not been used for more than two years, it may have been deleted and cannot be reopened.^5^
• Do not post the complete address, passwords, verification codes, purchase information, or other identifying details in this public thread.

References

1. Block an email address from signing in
2. My username and password have stopped working | Microsoft Support
3. Get Help for Microsoft personal account users | Microsoft Support
4. Contact Microsoft customer support | Microsoft Support
5. I can't sign in to my Microsoft account | Microsoft Support