Correct approach: display a warning that says something like "We think you've mistyped your email address. Please re-enter it, otherwise click 'submit' if you

Correct approach: display a warning that says something like "We think you've mistyped your email address. Please re-enter it, otherwise click 'submit' if you think we're wrong :)" I'm tired of sites not accepting perfectly valid symbols like "+" in my email address.