I have a DLL library, which I have no control over, that builds a XML message and sends it over HTTP to a web server. Due to the strict specifications, the server will only accept message with POST HTTP/1.1. However, the logs in the server shows receiving messages being POSTed HTTP/1.0. If I open the URL directly into a browser, the log shows GET HTTP/1.1, which is correct. We're not going through a proxy and the gateway isn't changing the version from what I can tell. I've tried on two different networks and I get the same error. Also, I have tried on Windows Server 2003 and Windows XP Pro, both of which should support HTTP 1.1.

Does anyone have any ideas why the server is receiving HTTP/1.0 using a POST, but using a GET shows HTTP/1.1?

Edit:
I've contacted the DLL maker about this, but their help isn't that great.

Edit 2:
Using Fiddler, I was able to extract the header, which is posted below. As you can see it's using HTTP/1.0.

POST /48A548C0BA8211DEA1EEE5AF2B3D5823;48A548C1BA8211DEA1EE8EF735B81699/
SJzWLaVEESCESCX6ESCESCW~ESC6FESCwxEuESCESCAb,L7ESCecvESCuESCESCrBESCHpESC3
ESCESCJw\_ESCESClrj,ESC\_4xESCOQpLwyRJGgp6p3YDG!uvXESCESC6!wVxESC7.dESCcTvmG5WM HTTP/1.0

Content-Type: application/xml;charset="utf-8"
Host: \*\*\*
Content-Length: 787