A POST request consists of a number of headers and a request body. When you submit a form, the browser URL encodes names and values of all form fields and then puts them in the request body in this format:
fieldname1=fieldvalue1&fieldname2=fieldvalue2
I.e. the request body looks like a typical query string.
Here's what the request could look like for your form:
POST /bugreport.php HTTP/1.1
Host: www.example.com
Content-Type: application/x-www-form-urlencoded
Content-Length: [size of the request body]
logfile=blabla&configfile=more+blabla&usercomment=hello&useremail=
To make sure your program matches what a browser would do, you can post the form with Firefox and then inspect the request headers and body using Firebug's net panel.
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