The HTML5 standard prescribes a regex for implementers to validate email addresses on the client side:

  /^[a-zA-Z0-9.!#$%&’*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$/

So if you're going to use <input type=email>, you might as well use the same check on the server side.