整合Mozilla的Email客户端Thunderbird和日程簿软件Sunbird。Mozilla Sunbird 参见这里，Mozilla Thunderbird 参见这里。

Lightning brings the Sunbird calendar to the popular email client, Mozilla Thunderbird. Since it's an extension, Lightning is tightly integrated with Thunderbird, allowing it to easily perform email-related calendaring tasks.

Lightning is a fairly new development. Its first public release was in early 2006. However, being based off of the same backend code as Mozilla Sunbird®, it is maturing quickly.

For the details of what's new in this release, please read the Lightning Release Notes.

Some goals for future releases are:

Even tighter Thunderbird integration
email-to-task linkage
Thunderbird address book integration
more robust iMIP support (meeting invitations)
more robust CalDAV support
offline calendar use
printing
device synchronization (Palm, PocketPC, iPod, phone, etc.)