Create a user using strict username sanitization: only alphanumeric, _, ., -, and/or @ are allowed.
This function runs when a user self-registers as well as when a Super Admin creates a new user. Hook to 'wpmu_new_user' for events that should affect all new users, but only on Multisite (otherwise use 'user_register').
<?php wpmu_create_user( $user_name, $password, $email ); ?>
wpmu_create_user() is located in