Yahoo and Google are introducing new versions of their Web-based software that compete with Microsoft's Outlook.

Yahoo's new Zimbra Collaboration Suite (ZCS) 5.0 allows users to read Microsoft Outlook e-mail alongside Yahoo Mail or Google's Gmail or Zimbra's own branded e-mail.

In effect, Zimbra's upgrade lets users read work and personal e-mail side by side.

Enhancements in ZCS 5.0 extend Zimbra's anywhere access on the desktop, including support for Microsoft Outlook 2007, and on virtually any device, with support for BlackBerry Enterprise Server, J2ME-enabled handsets such as the Motorola RAZR, and a new version of ZCS for mobile web browsers. New features in the Zimbra AJAX Web client include instant messaging, briefcase, and task applications as well as Zimbra Desktop, the first offline-capable Web 2.0 application.

"We really think this is the next generation of Outlook that we are announcing," said Satish Dharmaraj, co-founder and chief executive of Zimbra.

The ZCS 5.0 Open Source Edition, available now, is free. The commercially supported ZCS 5.0 Network Edition is available for a 60-day free trial on the Zimbra Website. Zimbra's Hosted Demo is available for an immediate test drive of ZCS, visit http://www.zimbra.com/demo.

Yahoo paid $350 million in September to buy Zimbra, a provider of e-mail, calendar and contacts software that competes with Microsoft and Google.

Around the same time, Google paid $625 million to acquire e-mail security firm Postini to beef up Google Apps to make it more useful inside businesses. Google Apps, a suite of software that competes with Microsoft Office.

Google's new applications deliver message filtering, encryption and archiving for any business environment. Google's new security services work with any mail system, including Lotus Notes, Microsoft Exchange, and Novell Groupwise, and pricing starting at $3 per user per year.

Google offers three packages. The Google Message Filtering service filters incoming spam and malware. Google Message Security includes Google Message Filtering, plus enhanced virus detection, outbound processing, and content policy management. Google Message Discovery includes Google Message Security, plus one year of message data archiving, retention, and discovery for companies seeking to reduce security exposure, and improve legal discovery readiness and message compliance.

The new packages are part of the Google Apps platform and are available immediately at www.google.com/a/security.

"We replace the old world of installing software and dealing with security patches and coming in late at night to restart computers," Scott Petry, founder of Postini in 1999 and now a Google product manager, said of his company's impact.