Seems that the best solution will be to have that page tell your browser not to cache it (use an HTTP Header called "Expires" or if you cannot configure the HTTP headers from your web server, add a META HTTP-Equiv for the same thing. Do google search like: http://www.google.com/search?q=HTML+header+meta+tag+cache to find out more).

Or you can put a link in the email with some random data at the end to invalidate a cache-match. i.e. call http://someserver/test.html as http://someserver/test?blahblah123123123blah

Find a good electronic resource on HTTP. That will help clear up cache-control solutions.

-- termix