How to create a Custom WooCommerce Email | https://www.ibenic.com/create-custom-woocommerce-email

class.php

<?php


/**
 * Class Custom_WC_Email
 */
class Custom_WC_Email {

	/**
	 * Custom_WC_Email constructor.
	 */
	public function __construct() {
    // Filtering the emails and adding our own email.
		add_filter( 'woocommerce_email_classes', array( $this, 'register_email' ), 90, 1 );
    // Absolute path to the plugin folder.
		define( 'CUSTOM_WC_EMAIL_PATH', plugin_dir_path( __FILE__ ) );
	}

	/**
	 * @param array $emails
	 *
	 * @return array
	 */
	public function register_email( $emails ) {
		require_once 'emails/class-wc-customer-cancel-order.php';

		$emails['WC_Customer_Cancel_Order'] = new WC_Customer_Cancel_Order();

		return $emails;
	}
}

new Custom_WC_Email();

email-content.php

<?php

class WC_Customer_Cancel_Order extends WC_Email {
  
  // ...
  
  /**
	 * Get content html.
	 *
	 * @access public
	 * @return string
	 */
	public function get_content_html() {
		return wc_get_template_html( $this->template_html, array(
			'order'         => $this->object,
			'email_heading' => $this->get_heading(),
			'sent_to_admin' => false,
			'plain_text'    => false,
			'email'			=> $this
		), '', $this->template_base );
	}

	/**
	 * Get content plain.
	 *
	 * @return string
	 */
	public function get_content_plain() {
		return wc_get_template_html( $this->template_plain, array(
			'order'         => $this->object,
			'email_heading' => $this->get_heading(),
			'sent_to_admin' => false,
			'plain_text'    => true,
			'email'			=> $this
		), '', $this->template_base );
	}
}

email-trigger.php

<?php
/**
 * Class WC_Customer_Cancel_Order
 */
class WC_Customer_Cancel_Order extends WC_Email {
  
  // ...
  
  /**
	 * Trigger Function that will send this email to the customer.
	 *
	 * @access public
	 * @return void
	 */
	function trigger( $order_id ) {
		$this->object = wc_get_order( $order_id );

		if ( version_compare( '3.0.0', WC()->version, '>' ) ) {
			$order_email = $this->object->billing_email;
		} else {
			$order_email = $this->object->get_billing_email();
		}

		$this->recipient = $order_email;


		if ( ! $this->is_enabled() || ! $this->get_recipient() ) {
			return;
		}

		$this->send( $this->get_recipient(), $this->get_subject(), $this->get_content(), $this->get_headers(), $this->get_attachments() );
	}
}

email.php

<?php
if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly
}

if ( ! class_exists( 'WC_Email' ) ) {
	return;
}

/**
 * Class WC_Customer_Cancel_Order
 */
class WC_Customer_Cancel_Order extends WC_Email {

	/**
	 * Create an instance of the class.
	 *
	 * @access public
	 * @return void
	 */
	function __construct() {
    // Email slug we can use to filter other data.
		$this->id          = 'wc_customer_cancelled_order';
		$this->title       = __( 'Cancelled Order to Customer', 'custom-wc-email' );
		$this->description = __( 'An email sent to the customer when an order is cancelled.', 'custom-wc-email' );
    // For admin area to let the user know we are sending this email to customers.
		$this->customer_email = true;
		$this->heading     = __( 'Order Cancelled', 'custom-wc-email' );
		// translators: placeholder is {blogname}, a variable that will be substituted when email is sent out
		$this->subject     = sprintf( _x( '[%s] Order Cancelled', 'default email subject for cancelled emails sent to the customer', 'custom-wc-email' ), '{blogname}' );
    
    // Template paths.
		$this->template_html  = 'emails/wc-customer-cancelled-order.php';
		$this->template_plain = 'emails/plain/wc-customer-cancelled-order.php';
		$this->template_base  = CUSTOM_WC_EMAIL_PATH . 'templates/';
    
    // Action to which we hook onto to send the email.
		add_action( 'woocommerce_order_status_pending_to_cancelled_notification', array( $this, 'trigger' ) );
		add_action( 'woocommerce_order_status_on-hold_to_cancelled_notification', array( $this, 'trigger' ) );

		parent::__construct();
	}
}

plugin.php

<?php
/**
 * Plugin Name: Custom WooCommerce Email
 */

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

template-plain.php

<?php
/**
 * Admin cancelled order email (plain text)
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/emails/plain/admin-cancelled-order.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.woothemes.com/document/template-structure/
 * @author  	WooThemes
 * @package 	WooCommerce/Templates/Emails/Plain
 * @version 	2.5.0
 */

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

echo "= " . $email_heading . " =\n\n";

echo sprintf( __( 'The order #%d has been cancelled. The order details:', 'woocommerce' ), $order->id ) . "\n\n";

echo "=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=\n\n";

/**
 * @hooked WC_Emails::order_details() Shows the order details table.
 * @hooked WC_Emails::order_schema_markup() Adds Schema.org markup.
 * @since 2.5.0
 */
do_action( 'woocommerce_email_order_details', $order, $sent_to_admin, $plain_text, $email );

echo "\n=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=\n\n";

/**
 * @hooked WC_Emails::order_meta() Shows order meta data.
 */
do_action( 'woocommerce_email_order_meta', $order, $sent_to_admin, $plain_text, $email );

/**
 * @hooked WC_Emails::customer_details() Shows customer details
 * @hooked WC_Emails::email_address() Shows email address
 */
do_action( 'woocommerce_email_customer_details', $order, $sent_to_admin, $plain_text, $email );

echo "\n=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=\n\n";

echo apply_filters( 'woocommerce_email_footer_text', get_option( 'woocommerce_email_footer_text' ) );

template.php

<?php
/**
 * Cancelled Order sent to Customer.
 */

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

/**
 * @hooked WC_Emails::email_header() Output the email header
 */
do_action( 'woocommerce_email_header', $email_heading, $email ); ?>

	<p><?php printf( __( 'The order #%d has been cancelled. Order Details:', 'woocommerce' ), $order->get_order_number() ); ?></p>

<?php

/**
 * @hooked WC_Emails::order_details() Shows the order details table.
 * @hooked WC_Emails::order_schema_markup() Adds Schema.org markup.
 * @since 2.5.0
 */
do_action( 'woocommerce_email_order_details', $order, $sent_to_admin, $plain_text, $email );

/**
 * @hooked WC_Emails::order_meta() Shows order meta data.
 */
do_action( 'woocommerce_email_order_meta', $order, $sent_to_admin, $plain_text, $email );

/**
 * @hooked WC_Emails::customer_details() Shows customer details
 * @hooked WC_Emails::email_address() Shows email address
 */
do_action( 'woocommerce_email_customer_details', $order, $sent_to_admin, $plain_text, $email );

/**
 * @hooked WC_Emails::email_footer() Output the email footer
 */
do_action( 'woocommerce_email_footer', $email );