is almost always a VERY BAD IDEA. Yet there are still apps out there doing
  this, and now recently it triggered a bug/side-effect in libcurl as when
  libcurl sends a POST or PUT with NTLM, it sends an empty post first when it
  knows it will just get a 401/407 back. If the app then replaced the
  Content-Length header, it caused the server to wait for input that libcurl
  wouldn't send. Aaron Oneal reported this problem in bug report #2799008
  http://curl.haxx.se/bug/view.cgi?id=2799008) and helped us verify the fix.