Tumbleweed Communications announced the release of Tumbleweed MMS 5.6. The company says that this new release offers enterprises new anti-spam management features providing improved visibility and feedback of spam-blocking efforts, and additional protection against email fraud and phishing scams via digital signing of email messages. Tumbleweed MMS works with corporate email servers such as Microsoft Exchange, Lotus Notes, Novell Groupwise and a variety of UNIX-based email servers.