recently i figured, SAP CPI very conviently omitted headers to its wish & created a feud between me and 3rd Party API server team(on a lighter note).
API Token was sent via HTTP connection but to my misfortune API server never validated/authenticated the request from SAP CPI. The bigger issue was when API server was stingy with logging process and never reflected the headers that should or could be captured. This left us in a limbo until we ventured to trigger HTTP request on to a public web service(
https://requestbin.com/) to read the "headers".
To my surprise, SAP CPI had decided to omit sending the header to
requestbin.
In order to fix this issue, One must explictily mention the headers that needs to be sent to the HTTP servers. This can be acheived under HTTP receiver > Connection Details > Request Headers. If in case there are multiple headers then it must be differentiated by a pipeline ("|")