I read "How do I back up Thunderbird emails?" from here.
How can I use it again when the account will be deleted from Thunderbird or change the operating system?
I read "How do I back up Thunderbird emails?" from here.
How can I use it again when the account will be deleted from Thunderbird or change the operating system?
The folder ~/.thunderbird includes everything you need. It includes emails, accounts, settings, (email-) passwords etc. If you simply backup the folder regularly, you can simply copy it back to your newly installed system, into ~/ (which is your home directory, /home/yourname).
Even the installed extensions, add-ons etc. will be available instantly in most cases, with no other action but simply copying back the (whole) backed-up ~/.thunderbird -folder into ~/.
Couldn't be easier :)