apply_filters( 'update_welcome_user_subject', string $subject )

1961	 * Filters the subject of the welcome email after user activation.1962	 *1963	 * @since MU (3.0.0)1964	 *1965	 * @param string $subject Subject of the email.1966	 */1967	$subject = apply_filters( 'update_welcome_user_subject', sprintf( $subject, $current_network->site_name, $user->user_login ) );1968 1969	wp_mail( $user->user_email, wp_specialchars_decode( $subject ), $message, $message_headers );1970 1971	if ( $switched_locale ) {1972		restore_previous_locale();1973	}