Checking against duplicate e-mail addresses.

<i><b>Originally posted by : Paul White (pw1972@hotmail.com)</b></i><br /><br />In my application I allow users to register with us, thus storing their information in the database. What I want to do is on Add's and Update's, is verify that the e-mail address the user has is unique to the system and someone else is not using it. I also want this to be client side verified so I don't have to reload pages everytime the user submits with a duplicate e-mail address. Herein lies my problem, I don't want to store the e-mail addresses in a giant javascript array, for the simple reason I don't want that list to be publicly available to any schmuck that can view the source code on the page. I've toyed with the idea of invisible frames and such, but ultimately with a little detective work you would still be able to view the source on the page and see the list of e-mail addresses. Any suggestions on how to do this? Wow, I guess this isn't really an ASP question, but what the hell, you're a pretty smart bunch.<br /><br />Ciao,<br />Paul