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",Process Integration 7.0, PI 7.0, PI 7.01, PI 7.02, Process Integration 7.10, PI 7.10, Process Integration 7.11, PI 7.11, Process Integration 7.30, PI 7.30, Process Integration 7.31, PI 7.31, Process Orchestration 7.40, PI 7.40, PO 7.40, Process Orchestration 7.50, PI 7.50, PO 7.50, NetWeaver, XI  , KBA , BC-XI-CON-AFW , J2EE Adapter Framework , BC-XI-IS , Integration Server , Problem