The web search giant has made another acquisition. Today, Google bought e-mail security company Postini for 625 million dollars in cash. Postini is producing a technology used to encrypt and archives e-mails and instant messages and it can be used to protect a company’s all web-based communications.

In this moment, according to a press release, Postini has more than 35,000 businesses and 10 million users worldwide.

"With this transaction, we’re reinforcing our commitment to delivering compelling hosted applications to businesses of all sizes. With the addition of Postini, our apps are not just simple and appealing to users -- they can also streamline the complex information security mandates within these organizations," said Eric Schmidt, Chief Executive Officer of Google.

The acquisition is expected to close by the end of the third quarter, the companies said today in a statement. Postini's technology could attract more companies to use Google's Gmail e-mail service, which is linked to other Google software for calendars, spreadsheets and instant messaging.

The acquisition of Postini is seen as sign of Google’s intention to advance further into the business software market, after it has acquired Silicon Valley startup Upstartle and Tonic System.

Google Apps, which includes Gmail, Calendar, Talk, Docs & Spreadsheets, and Personal Start Page, has been adopted by more than 100,000 businesses already.

"For Google customers this is a clear statement that we are very committed to this business," Dave Girouard, general manager of Google Enterprise, said on a conference call with analysts. "We are going to continue to innovate and bring more and more applications and services to businesses.