HTML5 Email input pattern attribute
I had this exact problem with HTML5s email input, using Alwin Keslers answer above I added the regex to the HTML5 email input so the user must have .something at the end.
<input type="email" pattern="[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}$" />
This is a dual problem (as many in the world wide web world).
You need to evaluate if the browser supports html5 (I use Modernizr to do it). In this case if you have a normal form the browser will do the job for you, but if you need ajax/json (as many of everyday case) you need to perform manual verification anyway.
.. so, my suggestion is to use a regular expression to evaluate anytime before submit. The expression I use is the following:
var email = /^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}$/;
This one is taken from http://www.regular-expressions.info/ . This is a hard world to understand and master, so I suggest you to read this page carefully.