Thanks for your replies @odanylewycz & @allenheltondev.
Yes, I’ve tried POST as well with Basic Auth using the base64 encoded string as mentioned and also body using form-data & x-www-form-urlencoded types in the pre-request script for auth_form request. It is basically the java spring security authentication that I’m trying to do in Postman. After this HTML form based auth request, I’ve to send the actualy POST request with json body to get a json response at a different endpoint.