3397990 - Internal server error failed to call the end point in soap channel when connecting to XI inbound proxy

You have configured a SOAP/RFC receiver communication channel to establish a connection to an XI inbound proxy with an RFC destination.

When the scenario is executed, the error message  ‘ internal server error failed to call the end point’ is displayed.

In the XPI inspector example 50 logs you may find:
Error in call over HTTP: HTTP 500 Internal Server Error
[EXCEPTION]
java.io.IOException: No SOAP Envelope. Data contains no valid soap namespace. Value in message is "". Required values are "false" or "http://www.w3.org/2003/05/soap-envelope".; HTTP 500 Internal Server Error
    at com.sap.aii.af.sdk.xi.net.HTTPClientConnection.call(HTTPClientConnection.java:1307)

SAP NW All versions

internal server error failed to call the end point, Error in call over HTTP: HTTP 500 Internal Server Error, No SOAP Envelope, no valid soap namespace, "http://www.w3.org/2003/05/soap-envelope", , KBA , BC-XI-CON-AFW , J2EE Adapter Framework , BC-XI-IS , Integration Server , Problem