You can't remove Lightning as it is built-in. But you can hide the Today Pane with the status bar control at the bottom right.

That's what I was afraid of. Thanks so much for your reply!

Yeah I have no use for the task/cal. either. I thought Mozilla prided it's self on being the free to have it your way instead of being forced fed useless options like what M$ does.

I noticed that there is a Google connection so I'm thinking there is money involved. Can't wait until I start getting ads in my inbox because I will want to see them to enhance my Thunderbird experience. 

If Mozilla is just run by volunteers then why don't you take into account that me and other people didn't volunteer for the useless calendar/task functions? Also is this just a form of spyware linked to Google analytics? Something just doesn't feel right here, you wouldn't embed this so deeply unless there is a underlying corporate issue or payout somehow. Why don't you come clean and tell your users why this is forced into the program.

Maybe as this becomes increasingly bloated and more complicated you could offer a lite version for people that just want to retrieve and send simple emails.

If I send you $50 bucks then can I remove the cal/task part?

Personally, I welcome calendaring being built-into the program. Previously, you had to install Lightning as an addon, then install an addon into the addon to give connection with Google calendar, for instance. That was very klunky and non-user friendly compared with the competition such as eM Client, not to mention Microsoft Outlook, and expected a lot of tyro end users. I take your point about bloat when it is functionality you do not need, but at least it can be hidden away and ignored -- just like 80% of the functionality in other programs that you don't use!

Lightning integration in V78 seems to create an actual bug. My customer booking system sends out emails with text messages as well as ICS files, and something in Lightning makes it that the text - ie the actual purpose of the email - cannot be seen in any way. In V68 I can remove Lightning to fix this, in V78 not. See my specific question:

https://support.mozilla.org/en-US/questions/1313033