https://xxx.de/Plugins/PaymentPayPalStandard/IPNHandler
IP 173.0.81.1 (host: notify.paypal.com)
builtin@search_engine_record.com
Tried everything including to fix but cannot succeed.
Using PaypalStandardPayment, PaypalPlusPayment and noptemplates OPC Checkout.
Pls. see
https://www.nopcommerce.com/en/boards/topic/84852/paypal-ipn-handler-400-bad-request