How To Fire Asp Page From An Email

We are sending an html email from asp page.In the email we
appended an image tag and the "src" attribute points an asp page in our
server.Here when ever user read the email this image tag will fire our
asp page.It is working fine if we open the mail in web browsers.It is
failing in outlook express.We modified the code a bit and replaced the
<imgtag with <iframetag.It is woring fine in outlook express now.
but it is not failing in web browsers.Do we have any other alternative
method to call an asp page from the email.