If you just want an empty window with the email id in it, you can either send it back to a simple servlet,
JSP, CGI etc. which builds the simple page:
<a href='myservlet?id=fred@onlinestuff.net'>fred@onlinestuff@net</a>
or open the window and populate it using JavaScript.
But I have to ask is this what you really want. Are you sure you don't actually want a mail client to pop up when you click on the link, alowing you to compose and send a message to the email address? If this is the case, you just need to put a link as follows, and the browser will do it for you:
<a href='mailto:fred@onlinestuff.net'>
fred@onlinestiff.net</a>