function isEmailAddress(string) {
    return /^[^@]+@[^.]+(\.[^.]+)+$/.test(string);
}

function validate(form) {
    var controls = form.elements,
        emailAddress = controls['Email'].value;
  
    /* Validate other controls */

    if (!isEmailAddress(emailAddress)) {
        alert('Please enter a valid e-mail address.');
        return false;
    }

    /* More validation */

    return true;
}