ASP CDO Mail Only Works When Browser Cache Is Cleared

I have a simple form on a page in my website in which a user can enter
an email address to be added to a mailing list.

The following ASP script works the first time a user submits his or
her email address. However, if the same user tries to submit another
email, the browser hangs and times out. If the user clears the
browser's cache, this script works fine. Could someone please explain
this behaviour and how I can resolve it?

<%
Set myMail=CreateObject("CDO.Message")
myMail.Subject= "MAILING LIST ADDITION"
myMail.From= Request.Form.Item(1)
myMail.To="user@domain.com"
myMail.TextBody= "Please add the following person to the mailing list:
" & VbCrLf & VbCrLf & Request.Form.Item(1)
myMail.Send
set myMail=nothing
Response.Redirect "http://www.domain.com"
%>