Using technology acquired from Postini last year, the Mountain View, Calif. search company has begun offering new spam filtering and message archiving options for businesses.

The cost of the program ranges from $3 to $25 per user per year depending on the level of functionality the customer desires. In addition, the features are compatible with any e-mail system, including Microsoft Exchange, Lotus Notes, and Novell Groupwise.

Google's move could be seen as a further effort to break into Microsoft's hold on business software. It first launched its enterprise effort in August 2006, and Tuesday's announcement is a continuation of that.

"As threats rise in volume and complexity, and compliance requirements pile up, IT is struggling to find the resources to keep up," product management chief Scott Petry said in a statement.

Postini was acquired by Google in July of last year for $625 million. At the time, CEO Eric Schmidt characterized the buy as a reinforcement of "our commitment to delivering compelling hosted applications to businesses of all sizes."

The basic product offers spam filtering, and costs $3 per user. The mid-range offering adds enhanced virus detection, outbound processing, and content policy management for $12 per user yearly, while the top-end product includes one year of archiving and retention for $25 per user per year.

Google says that its Google Apps program is used by more than 500,000 businesses and thousands of universities. More information on the program's features can be found on the Google Apps website.