Hello, thank you for reaching out to Microsoft Q&A.
Could you please let me know exactly where you are seeing this unknown email address?
- Do you see it when you sign in with your Microsoft account (for example, when verifying your identity)?
- Or is it listed as an alias (an additional email address) on your Microsoft account?
- If the unknown email is listed as an alias, you can remove it by signing in to your Microsoft account here:
https://account.live.com/names/manage
*If the unknown email is listed as an alternate security/recovery method, you can manage and remove it by signing in to your security info here: https://account.live.com/proofs/Manage
Before removing it, please make sure you have other valid security verification methods (such as your correct Outlook email address or phone number) added to your account, so you don’t lose access.