This week Google announced the acquisition of Postini, a communications security and compliance company, for US$ 625 million. Google has made inroads into the enterprise and higher education markets with notable additions to their Google Apps offering. But Postini's capabilities are an entirely different value proposition, making the search giant into a contender for the long, arduous battle with legal and corporate compliance concerns."We realized that we needed a more complete way to address these information security and compliance issues in order to better support the enterprise community," said VP and General Manager Dave Girouard of Google Enterprise. "That’s why we’re excited to share the news that we’ve agreed to acquire Postini, a company that offers security and corporate compliance solutions for email, IM, and other web-based communications."Postini features on-demand communications security and compliance solutions on a wholly-hosted service model, or SaaS. It serves over 35,000 businesses and 10 million users. Email and IM management services include inbound and outbound policy management, spam protection, virus guard, content filtration, message archiving and encryption, among other offerings. Postini's suite of compliance solutions, including encryption, archival and policy-enforced TLS, make it an attractive package for enterprises seeking respite from e-Discovery and SOX neurosis.Specifically, Postini's capabilities can be used to add much-needed bulk to Google Apps Premier Edition, which includes Gmail, Calendar, GoogleTalk, Docs, Spreadsheets and Personal Start Page. In an ideal world, these can all be strengthened with the inclusion of real security and -- Gmail users cheer! -- dedicated spam guard. (Gmail is insanely spammy.) Not to say that Apps hasn't made inroads on its own merit. In February, Google toted Apps as a response for space-hungry ITs seeking free servers to fill. Not exactly a benign glide into the business space. According other recent quotes by Girouard, Google Apps is gaining "more than 1,000 small businesses every day." Google was already using Postini alongside their Gmail offering, so the transition will likely be a rather natural one. Nonetheless, the acquisition was a surprise for some who heard rumor that the company was aiming for its own IPO.C|Net, which looks at the Gmail/Postini tryst as an outsourced model, added, "Large companies won't outsource e-mail without security while mid-market companies want turnkey bundled solutions. Now Google has all of the pieces in hand."Well, isn't that something. And lest we forget to mention the obvious, the Postini acquisition is also a clear jab in Microsoft's direction. The software Goliath has a grapplehold on the enterprise email scene, which if things keep up this way, may not be the case in a few years. The acquisition will be finalized in calendar Q3 of this year. Got a view on it? Do share.