Although I agree with the meta-point, there's still value in doing some basic validation. If there's no @ sign, or the domain name looks like it was mistyped (gmali, yahhoo), then a better user experience for your user is to present them with a warning and ask them to retype their email. You may not want it to be a blocking warning (that is you can still submit the form), but some validation can be a huge value add to users.

Still, sending an email beats regex validation any day for determining it's a real, working address.