Notify user of signup success.
This is the notification function used when no new site has been requested.
Filter 'wpmu_signup_user_notification' to bypass this function or replace it with your own notification behavior.
Filter 'wpmu_signup_user_notification_email' and 'wpmu_signup_user_notification_subject' to change the content and subject line of the email sent to newly registered users.
<?php wpmu_signup_user_notification( $user, $user_email, $key, $meta ); ?>
wpmu_signup_user_notification() is located in