Adds a "Create an account" section to WooCommerce guest customer emails

wc-email-create-account-section.php

<?php
/**
 * Adds a "Create an account?" section to customer emails
 * Only added for emails sent to guest purchases
 *
 * @param \WC_Order $order the order object
 * @param bool $sent_to_admin false if emails are sent to customers
 * @param bool $plain_text false for HTML emails
 */
function sv_add_email_register_section( $order, $sent_to_admin, $plain_text ) {

	$my_account_url = get_permalink( get_option( 'woocommerce_myaccount_page_id' ) );

	// bail if the account page endpoint isn't set or if this is an admin email
	if ( ! $my_account_url || $sent_to_admin ) {
		return;
	}

	// only add this section for guest users who will return false
	if ( ! $order->get_user() ) {
		
		ob_start(); 
	  
		?>
		<h3 style="text-align: center;">Save Time on Every Order</h3>
		<div style="text-align: center; margin-bottom: 2em;">
			<p>Want us to remember you for next time? You can easily register an account to set preferred shipping and billing addresses, securely save payment methods, and view your complete purchase history. It takes less than 20 seconds, and will make shopping fabulously easy!</p>
			<a href="<?php echo $my_account_url . '?email=' . urlencode( $order->billing_email ); ?>" style="border: 2px solid #a46497; border-radius: 5px; max-width: 400px; margin: 0.5em auto; padding: 10px 30px; text-decoration: none;">Create My Account</a>
		</div>
		<?php
		
		echo ob_get_clean();
	}

}
add_action( 'woocommerce_email_order_meta', 'sv_add_email_register_section', 50, 3 );

Upon inspection I found that it stoped working due to $order->billing_email being deprecated. Use $order->get_billing_email() instead.