How to Receive Outlook Invitations in Thunderbird
Thunderbird is an open source email client designed by Mozilla. The program provides many of the same email management and productivity functions as Microsoft Outlook, but lacks some key components out-of-the-box. Most notably, Thunderbird does not include calendar functionality for managing appointments and responding to meeting invitations. However, Thunderbird, like the Mozilla-designed Firefox Web browser, is built in a modular fashion and features a robust library of add-ons that can be installed to extend the capabilities of Thunderbird. The "Lightning" extension for Thunderbird is one such add-on that is intended to provide the missing calendar features and allow for seamless interaction with Outlook invitations.
Select "Tools," then "Add-ons" to open the extensions management pane.
Launch your Web browser.
Navigate to Lightning (see "Resources").
Drag the "Download Now" button from your Web browser into the Thunderbird extensions management pane to install the add-on.
Click "Install Now" to confirm installation of Lightning.
Restart Thunderbird. Invitations sent from Outlook will now be displayed with "Accept" and "Decline" buttons which will prompt an email response if needed. Accepted invitations will be added to your calendar within Thunderbird.