apply_filters( 'user_registration_email', string $user_email )

3495	 * Filters the email address of a user being registered.3496	 *3497	 * @since 2.1.03498	 *3499	 * @param string $user_email The email address of the new user.3500	 */3501	$user_email = apply_filters( 'user_registration_email', $user_email );3502 3503	// Check the username.3504	if ( '' === $sanitized_user_login ) {3505		$errors->add( 'empty_username', __( '<strong>Error:</strong> Please enter a username.' ) );3506	} elseif ( ! validate_username( $user_login ) ) {3507		$errors->add( 'invalid_username', __( '<strong>Error:</strong> This username is invalid because it uses illegal characters. Please enter a valid username.' ) );