Email Customizer: For making the template rtl css: yourtheme/woocommerce/emails/email-styles.php.

Email Customizer: For making the template rtl css: yourtheme::woocommerce::emails::email-styles.php

<?php
/**
 * Email Styles
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/emails/email-styles.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see     https://docs.woocommerce.com/document/template-structure/
 * @package WooCommerce/Templates/Emails
 * @version 3.3.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

// Load colors.
$bg              = get_option( 'woocommerce_email_background_color' );
$body            = get_option( 'woocommerce_email_body_background_color' );
$base            = get_option( 'woocommerce_email_base_color' );
$base_text       = wc_light_or_dark( $base, '#202020', '#ffffff' );
$text            = get_option( 'woocommerce_email_text_color' );

// Pick a contrasting color for links.
$link = wc_hex_is_light( $base ) ? $base : $base_text;
if ( wc_hex_is_light( $body ) ) {
	$link = wc_hex_is_light( $base ) ? $base_text : $base;
}

$bg_darker_10    = wc_hex_darker( $bg, 10 );
$body_darker_10  = wc_hex_darker( $body, 10 );
$base_lighter_20 = wc_hex_lighter( $base, 20 );
$base_lighter_40 = wc_hex_lighter( $base, 40 );
$text_lighter_20 = wc_hex_lighter( $text, 20 );

// !important; is a gmail hack to prevent styles being stripped if it doesn't like something.
?>
html,body,table, div,p,td,.em-main {
    direction: rtl !important;
}
td,th.td,.em-unsubscribe,
.em-image-caption-content{
text-align:right !important;
}
<?php