Thunderbird includes the Mozilla calendar engine, which is optimized to work within the email client.
While some of the software's future goals have yet to be implemented, there's still a lot to like about Mozilla Lightning Project. For example, the software promises better Thunderbird integration, emailtask linkage, integration with the Thunderbird address book, and support for meeting invitations (iMIP), to name just a few features.
Other noteworthy features of the software include improved CalDAV support, cached calendar support for offline use, and device synchronization.
It's also worth noting that Mozilla Lightning Project is available in editions for Linux and Windows, so you can use it no matter what platform you're running.
Overall, if you're in the market for a calendar and task management tool that is well-integrated with your email client, Mozilla Lightning Project is a solid choice.
Version 0.9: N/A