Google on Tuesday began marketing new online tools for protecting email from spam and other problems as it continued to encroach on the terrain of software king Microsoft.

Google unveiled email security services built with technology from Postini, a start-up the California Internet titan bought last year for 625 million dollars. The software protects, filters, encrypts and archives email, and is compatible with Microsoft Exchange, Lotus Notes, and Novell Groupwise.

Google said subscription pricing for email security starts at three dollars a year per user to "accommodate the budget of any business." Premium online services that include virus protection and saving messages is priced at 25 dollars annually per user.

"As threats rise in volume and complexity, and compliance requirements pile up, IT is struggling to find the resources to keep up," said Google director of product management Scott Petry. "Now, Google can take care of this for you."