We have resolved the issue. Actually the issue was not with the POST request and nor with the collector. We had a lambda code in a firehose which read the input data from the kinesis stream, once it came into collector and puts into S3. There was an issue with the lambda code which did not read the POST data and was rejecting it. We have implemented lambda earlier for the GET requests only however since POST requests comes in a different way (in the body and not as query string), we had to handle it differently in the same lambda. Now everything is working fine. Thanks for anyone who had helped.