Hello
Can you sign into your personal account via this link: https://account.live.com?
If so, 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.
Once added, make this new alias your primary alias, then you can delete the other email as alias, and that email is free from this Microsoft account instantly.
Then go to Security > Manage How I sign in, and update here too.
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If you cannot get into the link above because it wants to send the code to an email you no longer have access to, look for an option like “Show more verification methods” to see if you have a backup (e.g., a phone number or alternate email).
If you don’t have access to any of the options listed, select “I don’t have any of these.” This will begin the recovery process. As part of that process, Microsoft will let you add new contact information — but only after a 30-day waiting period.
This 30-day delay is intentional. It’s a security safeguard designed to protect users in case someone else tries to hijack their account by changing recovery info. The wait gives the rightful owner time to notice and stop unauthorized changes.
Unfortunately, this policy cannot be bypassed. Microsoft explains it further here.
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Once it is all updated, it should take about 24-48 hours for it to automatically sync on the Windows sign in.