Please clarify. As I understand it, you deleted messages in recent weeks and want to recover them? Thunderbird would only have them in the Trash folder, unless the trash folder hs been emptied.

Yes, I think I have a similar 'problem'. I seem to have accidentally deleted all my e-mails in a folder. I clear the deleted file every night before I log off.

What about the big man in the Cloud?! Would he have them? - If so, How do I get access?

Ta.

Thunderbird has no automatic backup. There are a number of products (many are free) that do provide cloud backup. Even there, always test a backup strategy to ensure it works. Many fail.

Thanks David, however I presume a new backup system can’t recover lost data from a previous time?

That is right. The problem that happens with backup software is that they often run while Thunderbird is active, and that results in an incomplete, corrupted, backup that isn't known until the user attempts to restore. I still use the old-fashioned backup strategy, exiting thunderbird and then copying the profile to a safe place.

here is the info in brief steps:

BACKUP

1. ensure thunderbird is not running
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media

RESTORE

1. ensure thunderbird is installed and NOT running
2. enter %appdata% in search window on task bar and press Enter key
3. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
4. start thunderbird and all should be there

Many thanks David. When I have time (!) I will try it. When you say T’bird ‘not running’, I presume it is okay to leave it on the taskbar, but just not opened?

NO. It's still running in the task bar.

Does that mean I have to remove the app?

No, just exit it. click the 'x' in upper right corner or click file>exit from menu bar