Microsoft prioritizes account security and works to prevent people from signing in without your permission. When we notice a sign-in attempt from a new location or device, we help protect the account by sending you an email message and an SMS alert. If your phone number or email changes, it's important to promptly update the security contact info on the Security basics page so we can work with you to keep your account secure and active.
If you sign in to your account while traveling or if you install a new app that signs in with your account, you may get an alert. We just need you to provide a security code so we know it was you, and that your account is safe.
To learn what you can do about unusual activity, select one of the following headings. It'll open to show more info.
If you're having problems signing into Windows or your Microsoft account, see When you can't sign into your Microsoft account for more info.
If you're looking for more info about how to improve security for your Microsoft account, see How to keep your Microsoft account safe and secure.
If you received an unusual activity notice while sending email in Outlook, see Unblock my Outlook.com account for more info.