title: Wordpress `wp_mail` fails with an HTTP error 500
body: <p>I'm using WordPress 3.0.1 on Windows 2003 32-bit running PHP 5.x with fastcgi on IIS6.</p>
  
  <p>I am using the <em>Contact Form 7</em> plugin for WordPress, and getting an HTTP 500 error on submit.  I am also getting HTTP 500 errors sending the test mail using the <em>Configure-Smtp</em> plugin.  I've narrowed it down to the <code>wp_mail</code> line in both cases.</p>
  
  <p>I can create a .php page in the same website and send an email using the php mail function, so I'm pretty sure PHP, IIS, and SMTP are all functioning.</p>
  
  <p>Firebug does not give me much in the way of useful info - I can paste the post and response headers if it would help.</p>