[Zope] Iterate all request input

[peter be]

Hello

I have a form page on a none-Zope site where a huge form sends lots of information about a visitors input to my Zope site, from where I send this with the sendmail tag.
If I knew exactly what input fields they post on the nonZope site, I could write something like this:
<dtml-sendmail>
To: email@someone.com
From: someemail@none.com

Firstname: <dtml-var firstname>
Nickname: <dtml-var lastname>
....
</sendmail>

The only problem is that I don't always know what fields they use on the nonZope site. So I can have maybe 5 or 30 input fields coming in to my Zope-sendmail.

In ASP one does something like this:
<% For each Request.Form in i
 request.form(i)
%>

But how is this done in DTML? And how do I prevent empty fields to cause problems? 
I also don't what to use <dtml-var nickname> since this might cause problems with existing objects called nickname in the namestack.