Manual:ResetUserEmail.php

Details
resetUserEmail.php file is a maint-scripts>Special:MyLanguage/Manual:Maintenance scripts|maintenance script to change the email address of users on the wiki, and mark the email address as confirmed. In addition to that, it will set a random password on that account. This will require the user to reset>Special:MyLanguage/Manual:Resetting passwords|reset his/her password in order to be able to login again.

This can be used to set or change an email address on an account that doesn't have a confirmed email address or the email address is no longer accessible. This can also be used to effectively lock an account by setting the email address to a fake one, since it also resets the password.