Historically I've kept lots of email locally on my laptop. This includes historical email, but also email with links, product license codes/keys, etc.
With my old laptop, I would clone my laptop regularly and copy my Outlook offline folders even more regularly to a thumb drive.
I got a new laptop and I can no longer use Outlook for my personal email, so I've switched to Thunderbird. I'd like to improve on my previous approach by using my OneDrive for these files, which should keep me from losing almost any mail.
Does anyone know of a process to move the offline TB folders in their default location to a One Drive folder? Is it as simple as copying them and changing where Thunderbird looks?
Outlook uses PST file, all your historical offline emails stored in this format.
You can copy this file and paste it in onedrive.
If you need to access this PST files form Thunderbird, you need to export them to Thunderbird format
refer this link
https://support.mozilla.org/en-US/questions/1270386