Based on technology obtained through Yahoo's Zimbra Software buyout in 2007, Zimbra Desktop can now provide e-mail access and offline synchronization to Yahoo Mail users on a choice of Windows, Linux, or Mac OS.

Yahoo Zimbra Desktop Beta is a free e-mail software that provides offline access to Yahoo Mail, Google Gmail and AOL Mail, through internet protocol support called Post Office Protocol (POP) and Internet Message Access Protocol (IMAP), at the same time and from the same place. Additionally, Yahoo Zimbra Desktop allows users to use the iCal standard to take their calendar offline.

Zimbra also lets you tag email and calendar items for easy search-and-find; and it provides a framework for creating "Zimlets," applets that allow mashups combining data from contact or calendaring information, for example, with maps or other data.

"Zimbra is focused on creating communication and collaboration solutions that ease the pain points of traditional e-mail, and switching between multiple e-mail accounts is one of the communication headaches that users encounter on a daily basis," said Satish Dharmaraj, Zimbra co-founder and Yahoo vice president. "With Yahoo Zimbra Desktop, we have taken our world-class collaboration suite and made it available for everyone for use anywhere, anytime, with any email account."

The software also features Zimbra Documents, a program that can be used to embed objects such as photos into documents and spreadsheets. It also can be used to create and edit documents and simple spreadsheets without having to switch between desktop programs or large e-mail attachments.

Zimbra Desktop, which is built on Mozilla Prism, is available for Windows, Mac and linux machines. It weighs in at 40 MB, about double the size of Thunderbird. The product promises the robust features of Outlook, which are lacking in Outlook Express and Thunderbird. Zimbra Desktop uses Java for crossplatform operability, along with Ajax browser technology for an enriched user interface.

Since the release of Beta 2 in April, Yahoo has broadened IMAP access to all users, not just those with "plus" accounts, enabling access not just to Yahoo Mail but also to other accounts such as Gmail and AOL that use IMAP or POP.