Another important step forward for all who are looking for alternatives to replace Outlook. With latest Thunderbird 2.0rc1 release it is now possible to add calendaring capability to Thunderbird (using the Lightning add-on) with Google calendar synchronization that works even with iCal invitations :-). Really nice.
Credits and thanks to Joel for finding it.
Author Miro Adamy
License (c) 2006-2019 Miro Adamy