get_checkout_payment_url( $on_checkout = false );

and:

$order->get_checkout_order_received_url();

if ( ! defined( ‘ABSPATH’ ) ) {
exit;
}

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