Managing personal Outlook.com account settings, security, and privacy
Hi,
If you received a single use code that you did not request, it could mean that someone accidentally entered your email address, or someone may be trying to access your Microsoft account.
If you did not request the code yourself, do not share or use the code. The good thing is that receiving the code alone does not mean your account has been accessed.
To help secure your account, I suggest the following:
• Change your Microsoft account password immediately and make sure it is strong and unique.
• Review your recent sign in activity here to check for unfamiliar login attempts: https://account.microsoft.com/security
• If you notice unfamiliar sign in attempts from unknown locations or devices, choose the option that says “This wasn’t me” on the activity page to report the activity to Microsoft.
As an additional security measure, please see “How to help keep your Microsoft account secure.”: https://support.microsoft.com/account-billing/how-to-help-keep-your-microsoft-account-secure-628538c2-7006-33bb-5ef4-c917657362b9