How to Validate email in drupal webfrom

To validate emails in drupal webfroms, simply add the following PHP code to web form settings (Additional Validation section)

  
<?php 

$email_address = $form_state['values']['submitted_tree']['email_address'];
if (!valid_email_address($email_address )) {
  form_set_error('submitted][email_address', t('The email address appears to be invalid.'));
}

?>