It's absolutely possible, but if you've never done this before it's not exactly an easy task. The gist is:
- You create a textbox input for the email
- You send whatever is in the textbox to a server via AJAX
There's a bunch of things to think about, like what if the player types in "asfdsagsdafdsafdsafds" and sends it? What do you do with it once it's on the server? A database perhaps? What if a player is evil and starts an SQL injection attack? What about privacy and stuff? Not to mention each question has more than one solution.