ASP Mailchimp Classic ASP Endpoint Error

I use the method described here:

http://apidocs.mailchimp.com/api/downloads/serialized_xml_listsubscribe.asps

I am using correct API Key and ListID. However, when I run the script, I get the following response:

"You must specify an email_address value for the listSubscribe method -90"

I have searched and mailed them but have not received a response yet. Someone had a similar problem - any thoughts on it there is a missing parameter?

Greetings.

Here's the code from the Mailchimp example:

Dim email
Dim apikey
Dim listId
Dim resp

email = Trim(Request.Form("Email"))
list_id = "xxxxxx"
apikey = "zzzzzzzzzzzzzzzzzzzzzz"

Dim xmlhttp
Set xmlhttp = Server.Createobject("MSXML2.ServerXMLHTTP")
xmlhttp.Open "GET","http://<my-dc>.api.mailchimp.com/1.3/?method=listSubscribe&output=xml&apikey=" & apikey & "&id=" & list_id & "&email=" & Server.URLEncode(email) & "&merge_vars=",false
xmlhttp.send
resp = xmlhttp.responsetext
Set xmlhttp = Nothing