apply_filters( 'wpmu_signup_blog_notification_subject', string $subject, string $domain, string $path, string $title, string $user_login, string $user_email, string $key, array $meta )

1007		 * @param string $title      Site title.1008		 * @param string $user_login User login name.1009		 * @param string $user_email User email address.1010		 * @param string $key        Activation key created in wpmu_signup_blog().1011		 * @param array  $meta       Signup meta data. By default, contains the requested privacy setting and lang_id.1012		 */1013		apply_filters(1014			'wpmu_signup_blog_notification_subject',1015			/* translators: New site notification email subject. 1: Network title, 2: New site URL. */1016			_x( '[%1$s] Activate %2$s', 'New site notification email subject' ),1017			$domain,1018			$path,1019			$title,