Order meta

function action_woocommerce_email_after_order_table( $order, $sent_to_admin, $plain_text, $email ) {
// Target certain email notifications
if ( in_array( $email->id, array( 'customer_on_hold_order', 'customer_processing_order', 'customer_completed_order' ) ) ) {
if ( $order->get_shipping_country() != 'Schweiz' ) {

    echo '<p><strong>Lieferung:</strong> '.$order->get_meta( 'pi_overall_estimate_min_date' ).' - '.$order->get_meta( 'pi_overall_estimate_max_date' ).'</p>';
}
}
}
add_action( 'woocommerce_email_after_order_table', 'action_woocommerce_email_after_order_table', 10, 4 );