Add BCC to WooCommerce emails - Add an email address (or two) as BCC to all WooCommerce emails. https://www.damiencarbery.com/2020/03/add-bcc-to-woocommerce-emails/

wc-add-bcc-to-emails-with-yith.php

<?php
/*
Plugin Name: Add BCC to WooCommerce emails (with YITH)
Plugin URI: https://www.damiencarbery.com/2020/03/add-bcc-to-woocommerce-emails/
Description: Add an email address as BCC to all WooCommerce emails. Updated for when YITH Request a Quote installed.
Author: Damien Carbery
Author URI: https://www.damiencarbery.com
Version: 0.1
*/


// YITH Request a Quote calls the pre-WooCommerce 3.7.0 parameter version of the 'woocommerce_email_headers' filter (with 3 parameters).
add_action( 'woocommerce_email_header', 'dcwd_add_bcc_to_woocommerce_emails_header' );
function dcwd_add_bcc_to_woocommerce_emails_header( ) {
	if ( class_exists( 'YITH_YWRAQ_Send_Email_Request_Quote' ) ) {
		//error_log( 'Class YITH_YWRAQ_Send_Email_Request_Quote exists.' );
		add_filter( 'woocommerce_email_headers', 'dcwd_woocommerce_email_headers_3', 10, 3 );
	}
	else {
		//error_log( 'No class YITH_YWRAQ_Send_Email_Request_Quote active.' );
		add_filter( 'woocommerce_email_headers', 'dcwd_woocommerce_email_headers', 10, 4 );
	}
}


// Simple wrapper around the newer 4 parameter version of the filter call.
function dcwd_woocommerce_email_headers_3( $header, $email_id, $email_for_obj ) {
	return dcwd_woocommerce_email_headers( $header, $email_id, $email_for_obj, null );
}

function dcwd_woocommerce_email_headers( $header, $email_id, $email_for_obj, $email_class ) {
	// Bcc this email address to *all* WooCommerce emails.
	$header .= 'Bcc: you@domain.com' . "\r\n";
	
	// Add another address to the Order Completed emails only.
	if ( 'customer_completed_order' == $email_id ) {
		$header .= 'Bcc: me@domain.com' . "\r\n";
	}

	return $header;
}

wc-add-bcc-to-emails.php

<?php
/*
Plugin Name: Add BCC to WooCommerce emails
Plugin URI: https://www.damiencarbery.com/2020/03/add-bcc-to-woocommerce-emails/
Description: Add an email address as BCC to all WooCommerce emails.
Author: Damien Carbery
Author URI: https://www.damiencarbery.com
Version: 0.1
*/


add_filter( 'woocommerce_email_headers', 'dcwd_woocommerce_email_headers', 10, 4 );
function dcwd_woocommerce_email_headers( $header, $email_id, $email_for_obj, $email_class ) {
	// Bcc this email address to *all* WooCommerce emails.
	$header .= 'Bcc: you@domain.com' . "\r\n";
	
	// Add another address to the Order Completed emails only.
	if ( 'customer_completed_order' == $email_id ) {
		$header .= 'Bcc: me@domain.com' . "\r\n";
	}

	return $header;
}