Ah I see - your form isn't set up to appear from the email that sent it?
In that case try modifying your frontpage submission code to look like

S-Email-Format="TEXT/PRE" S-Email-Address="YourEmailAddressHere@somewhere.com"
B-Email-Label-Fields="TRUE" B-Email-ReplyTo-From-Field="TRUE" S-Email-ReplyTo="Email" B-Email-Subject-From-Field="TRUE" S-Email-Subject="subject"

That in theory should take the value of your 'Email' field, and set it as the 'reply to' address.

For further information visit:
http://www.prowebsites.net/frontpage...sion_Email.asp
The aim of that tutorial isn't quite the same, but I think the code is the same.

The code above also sets the subject line, so you might want to ditch that part.

After that you should be able to use the outlook rule I mentioned.