A left field reply; I find this email validation very good:
email=document.addUser.eMail.value;
var expression=/^([a-zA-Z0-9\-\._]+)@(([a-zA-Z0-9\-_]+\.)+)([a-z]{2,3})$/;
if(!(expression.test(email)) )
{
alert("Please enter a valid email address");
document.addUser.eMail.select();
document.addUser.eMail.focus();
return false;
}
This looks like a fairly good domain suffix list:
http://www.norid.no/domenenavnbaser/domreg.html
Wind is your friend
Matt