Lightning is a Thunderbird extension that adds calendar functions to the email client. Here's how to install it.
- Go to the Tools menu and click Add-ons to open the Add-on window.
- In the Search All Add-ons box, type Lightning.
- Click on the Lightning extension.
- Click the Add to Thunderbird button
A message asking you to verify that you chose the correct extension appears.
- After a four-second delay, you can click the Install Now button. Or, you can click the Cancel button at any time.
- Once installation is complete, restart Thunderbird.
You can learn more about Lightning by going to the Lightning Project