The Webhook widged says that the request are made from Blynk Server Side. This means that this method shouldnt work for my case because the Receiver is only recheable in my local Wifi Network.
I already tried to use a http client but then Blynk stops working.
You should be able to redirect WAN traffic to it via router settings. And/or just install your own Local Blynk Server. https://github.com/blynkkk/blynk-server
Not sure I understand your options then. Blynk is server based, and it’s email and Webhook methods are well established.
WiFi is available (on specific MCUs/adapters), but it connects your Blynkified hardware to the Internet & Blynk Server.
If you know what you are doing, then I suppose you could rig up a 2nd WiFi device to act as a bridge between your Blynk MCU and your AV receiver, but that would be outside of this forum’s purpose and seems more complicated than my initial suggestion for simple router forwarding.