Log on to your email account at outlook.office.com in a browser.

Select your avatar or initials on the far right side of the menu bar to open your My Account screen.

Press View account.

Select the Security tab at the top of the My Account screen.

Choose Update Info in the Update your security info area.

Verify your identity, if asked to do so. For example, you may be asked to enter a code sent to your phone number, if you previously entered a recovery phone number.

Select Add security info.

Choose An alternate email address or Phone Number from the first drop-down menu.

Enter an email address to serve as your recovery email address for your Microsoft account.

Press Next. Microsoft will email the new recovery address with a code.

Enter the code from the email in the Code area of the Add security info window. 

Press Next to save the changes and add the recovery email address to your Microsoft account.