How do I get __doPostBack if it's not on the page?

I have a very simple contact form page that doesn't even have any controls on it. It has input text boxes that I would like to handle in my code-behind. I'm trying to invoke __doPostBack on my input button that looks like this:

<input type="text" name="email" value="" /> ...
<input type="image" src="images/submit.gif" alt="Submit" onclick="javascript:__doPostBack('sendemail', 'name,company,email,phone,category,budget,message,urgent');" />

The problem is that when I look at the HTML source code, __doPostBack isn't even on there- so submitting my form gives a Javascript error of "Object Expected". I don't want to put any .NET controls on the page because most of the page is administrated by an html editor, which obviously can't understand or create .NET controls. How do I register the __doPostBack function on there? I plan to do this from my BasePage that other pages use but don't know how.Start Free Trial