gistfile1.php

<?php
/**
 * Filter the content of the notification email for new user signup success.
 *
 * @since MU
 *
 * @param string $content    Content of the notification email.
 * @param string $user       User login name.
 * @param string $user_email User email address.
 * @param string $key        Activation key created in wpmu_signup_blog().
 * @param array  $meta       By default, contains the requested privacy setting and lang_id.
 */
$message = apply_filters( 'wpmu_signup_user_notification_email',
	__( "To activate your user, please click the following link:\n\n%s\n\nAfter you activate, you will receive *another email* with your login." ),
	$user, $user_email, $key, $meta
);