public static function fix_email($email)
    {
        $parts = rcube_utils::explode_quoted_string('@', $email);
        foreach ($parts as $idx => $part) {
            // remove redundant quoting (#1490040)
            if ($part[0] == '"' && preg_match('/^"([a-zA-Z0-9._+=-]+)"$/', $part, $m)) {
                $parts[$idx] = $m[1];
            }
        }

        return implode('@', $parts);
    }