Just reiterating what Himanshu said. I had a quick google of your error response and it looks like this response could be due to a number of points. Could you please provide the full URL (URI + hostname name) of your POST request?
To comply with security concerns please change a couple of alpha chars in the servername (but dont use special chars) and dont provide the auth details. The issue has occurred before because an underscore character (or an unencoded space character) was used in a hostname, hence the reason im asking for hostname details. We need to understand the payload youre posting as well as the full parameters your using (matrix, template/uri, header and query parms) on the POST request as well as the payload and headers of your response please.
if this helped answer the post, could you please mark it as 'solved'? Also if you consider whether the title of your post is relevant? Perhaps if the post is solved, it might make sense to update the Subject header field of the post to something more descriptive? This will help people when searching for problems. Ta