MOUNTAIN VIEW, Calif. (AP) - Google Inc. is adding more e-mail security and storage products for businesses, sharpening its aim on a Microsoft Corp. stronghold while the competition between the two rivals also heats up in Internet search and advertising.

The tools to be introduced Tuesday build upon technology that Google acquired last year when it bought e-mail specialist Postini Inc. for $625 million. The package of products are designed to weed out junk mail and potential viruses as well as protect against leaks of confidential information sent through e-mail. Google also is offering to retain e-mail data for longer periods.

Google bought Postini largely to address concerns that its corporate e-mail service lacked adequate security and compliance measures.

All the latest features are compatible with Microsoft Exchange as well as Lotus Notes and Novell Groupwise. Prices will range from $3 per user to $25 per user, depending on how much protection and data retention a customer wants.

Google's push into business software, launched in 2006, looms as a threat to Microsoft, which derives much of its profit from the sale of its more expensive Office suite of software applications as well as its e-mail programs.

Meanwhile, Microsoft hopes to close the gap with Google in the lucrative Internet search and advertising market by buying their common rival, Yahoo Inc., for more than $40 billion.

If Yahoo accepts the unsolicited offer and the deal is approved by antitrust regulators, Microsoft would increase its share of the worldwide search market to about 16 percent, up from 3 percent currently, according to comScore Media Metrix. Google's share stands at 62 percent.

Without providing a breakdown, Google says hundreds of thousands of businesses, government agencies and schools already use its software applications. That includes users of free programs that are less sophisticated than the ones sold in a subscription package.