Yahoo! Zimbra Desktop is a next-generation email application that makes email easy again.
Key features

• Email, contacts, and calendar all in one application
• Available for Windows, Apple, or Linux desktop computers
• Easily set up Zimbra, Yahoo! Mail Plus, AOL and Gmail email accounts with the Account Wizard
• Any POP or IMAP email account can be added to Zimbra Desktop
• No limit to the size of your email storage
• It works online and offline

As with any Beta product, please use Zimbra Desktop at your own discretion. We do not recommend Zimbra customers run Zimbra Desktop Beta in production.