Backup Thunderbird email and address book

I want a real backup of my Thunderbird, both the mail and the address book, before a system reinstall and I keep reading conflicting advice about what to copy.

What is the complete and correct thing to back up?

The conflicting advice comes from people backing up pieces, when the correct answer is one thing: the profile folder, which holds mail, address book, settings, filters and account setup together. Back up the profile and you have backed up everything.

1

Find the profile: Help, More Troubleshooting Information and beside Profile Folder click Open Folder, which opens your profile in the file manager. This is the folder that matters, named something like xxxxxxxx.default beside a Profiles path.

2

Close Thunderbird completely before copying, so nothing is mid write, then copy the entire profile folder to your backup location, an external drive or cloud storage. The whole folder, not selected pieces, since the mail in Mail and ImapMail, the address book abook files, the filters and the account settings all live inside it interdependently.

3

To restore after the reinstall: install Thunderbird, let it create a fresh profile once and close it, then replace the new profile folder's contents with your backup, or point Thunderbird at the backup through the Profile Manager, thunderbird -P, creating a profile that uses the backed up folder.

4

Verify by opening Thunderbird and confirming mail, address book and settings all returned, the single folder having carried the entire Thunderbird world across the reinstall.

For a portable single file backup rather than a folder copy, the ImportExportTools NG add-on exports mail and the address book exports to CSV or vCard separately, useful for moving pieces to another application, but for a genuine backup and restore of Thunderbird itself the profile folder copy is complete and reversible in a way piece by piece exports are not. The MozBackup style tools automate the profile copy for those wanting a wizard, doing the same thing underneath.

Copied the whole profile folder as one thing, reinstalled, pointed Profile Manager at it and everything came back, mail, my address book, filters, all of it. I had been about to export mail and contacts separately and would have lost my filters and account setup. One folder was the answer.