What do you think of this solution? If email exists I reset this and I write old email. there is a way to cancel the form-post and / or return a custom error message??

function my_verify_and_reset_email($user_data) {
	if (isset($_POST['user_email'])) {
		$user_info = get_userdata($user_data['ID']);
		$old_email = $user_info->user_email;
		if(email_exists($_POST['user_email'])) {			
			$user_data['user_email'] = $old_email;
		}        
    }
	return $user_data;
}
add_filter('wpuf_update_profile_vars', 'my_verify_and_reset_email');

The problem is the conflict with “WP User Avatar” plugin. The max file size settings of this plugin conditions the max file size of WP User Frontend Pro. Suggestions?