Interesting use of Apache Derby (which originated with IBM Cloudscape)
The download includes the Apache Derby database, which acts as a local e-mail store, said Satish Dharmaraj, the company's CEO. Future versions will not require users to do the manual download, he said.
The first release of Zimbra Desktop is an alpha version. The beta version, due this summer, will work with POP and IMAP e-mail servers and will include access to the company's calendaring server. When the company releases its 5.0 product, it will include the offline capabilities.