Correct to create content for the text version separately, and separately for html-version. But these changes in the two lines do not fit.
replace byPHP Code:
$mline .= $basket->fields['customers_basket_quantity'] . ' x ' . $products->fields['name'] . "\n";
$mline .= ' <blockquote><a href="' . zen_catalog_href_link(FILENAME_PRODUCT_INFO, 'products_id='. $basket->fields['products_id']) . '">' . zen_catalog_href_link(FILENAME_PRODUCT_INFO, 'products_id='. $basket->fields['products_id']) . "</a></blockquote>\n\n";
PHP Code:
$mline .= $basket->fields['customers_basket_quantity'] . ' x ' . '<a href="' . zen_catalog_href_link(FILENAME_PRODUCT_INFO, 'products_id='. $basket->fields['products_id']) . '">' . $products->fields['name'] . '</a>' . "\n";