Not sure about the "Administrateur" directory, but Thunderbird stores different parts of the same profile in different locations depending on the nature of the data, i.e. you may have permanent data such as account settings and mailboxes in one of those locations, while temporary and cache data is kept separately in the other. You cannot choose one over the other because they're different parts of the same profile.

Yes, after making this post I have see this one on the right https://support.mozilla.org/en-US/kb/dangerous-directories-Thunderbird-account-settings

So it mean this is normal, and can't be avoided ?

For the "Administrateur" IDK where it's from, it's a new install, windows and Thunderbird, but I think at least this one can be avoided.

Yes, after making this post I have see this one on the right https://support.mozilla.org/en-US/kb/dangerous-directories-Thunderbird-account-settings , it's exactly ly problem, with my error message.

So it mean this is normal, and can't be avoided ? For me not a good idea ...

For the "Administrateur" IDK where it's from, it's a new install, windows and Thunderbird, but I think at least this one can be avoided.

It's unclear to me why that would be a problem you'd like to avoid or how that might cause you to lose your mail when making backups… Sounds like you've been ignoring that warning not knowing what it meant… But anyway, to answer your question, yes, that's how it works… And shouldn't be a problem unless you do things you shouldn't… :)

I have many folder, and it can explain why when I use a backup tool, I loose all my e-mail.

%APPDATA%\Thunderbird\Profiles\ is the only one you need to backup. That doesn't mean you should delete the other folders. They are there for reason. I don't understand why you'd lose all your mail when backing up the profile though. May be you're doing something wrong? Also see https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

%APPDATA%\Thunderbird\Profiles\ is the only one you need to backup.

Justly no. It's that I m seing all the time on post but if you do that, you loose all your mails, you will save only settings

- C:\Users\Me\AppData\Roaming\Thunderbird\Profiles (the result of %APPDATA%\Thunderbird\Profiles\) contain only settings - C:\Users\Me\AppData\Local\Thunderbird\Profiles contain mails

And the other one, idk why it was created, but I can remove it.

As explained on the link before, there is 2 (at least, 3 ATM on my side) folders to backup, and for me it's something stupid, it's for why I m asking if it's normal, or a problem on my installation, but it seem to be the new working mode.

It's that I m seing all the time on post but if you do that, you loose all your mails, you will save only settings

This can happen if you deliberately move the mail storage to a location outside of your profile. Did you? Check the 'Local Directory' setting in your Account Settings for each account.

C:\Users\Me\AppData\Local\Thunderbird\Profiles

Contains primarily cache data, and no mail. The whole point is to store cache data outside of the profile, so that the cache doesn't get backed up along with the profile.

C:\Users\Me\AppData\Local\Thunderbird\Profiles contain mails

I doubt that. If it really does for you, then it's because of something you did - for whatever reason.

C:\Users\Me\Administrateur\Application Data\Thunderbird\Profiles

Presumably something you created as well. May be that's your mail storage location? Up to you to delete it or not. But prior to deleting, I'd check what's in there.

For the moment I have mixed and removed C:\Users\Me\Administrateur\Application Data\Thunderbird\Profiles to use only C:\Users\Me\AppData\Local\Thunderbird\Profiles (as C:\Users\Me\Administrateur is useless , never used, only thunderbird use it)

So I have now 2 folder to backup.

Previously Thunderbird was using C:\Users\Me\AppData\Roaming\Thunderbird\Profiles to store mails ? So it can explain another problem. When I have restored my backup Thunderbird was not able to store mail with the message "not enought disk space", I think the error message happen because it was trying to use the "forbidden folder for security" so I have created a new account, I think it was the C:\Users\Me\Administrateur\Application Data\Thunderbird\Profiles

And I think I have loose my mail because the application have just saved C:\Users\Me\AppData\Roaming\Thunderbird\Profiles I have older mails before 2010 for exemple (stored in C:\Users\Me\AppData\Roaming\Thunderbird\Profiles), I just miss recent one.

When I have restored my backup Thunderbird was not able to store mail with the message "not enought disk space", I think the error message happen because it was trying to use the "forbidden folder for security"

Nope. If you check the article describing that issue, you'll see the error message you'd get in that case would be "The Local Directory path is not suitable for message storage", nothing to do with disk space.

And I think I have loose my mail because the application have just saved C:\Users\Me\AppData\Roaming\Thunderbird\Profiles

First off, unless you do something very, very wrong, the only way you may lose data because of a backup is if you restore from an old backup to overwrite newer data, or if you use a folder from the backup to overwrite a folder with the same name but in a different place and hence not really the same (hint hint), or something like that, never as a result of making the backup.

Even if what you say there, which doesn't really make sense, was correct, for that to happen you would still have had to overwrite newer data with old data from a backup, but that couldn't have happened if the newer data wasn't being stored there in the first place…

Or just forget to backup one of the multiple/random folders Thunderbird use for profiles ? Seriously there is others app that do same ? I m agree, I have a bad english but I repeat I have not overwrited folder, recents mail are not in the backup (and when a say backup, it's backups files), seriously I haven't searched all my "users" folders and I think the application have missed it too.

For exemple the folder choosed by Thunderbird C:\Users\Me\Administrateur\ is NEVER used, it's alone inside.

The application are probably just forget to backup a folder.

Nope. If you check the article describing that issue, you'll see the error message you'd get in that case would be "The Local Directory path is not suitable for message storage", nothing to do with disk space.

Os so was a bad planet alignement, because the folder size are less than 500M.

But I have saved a mail in an old profile to test 5 mn ago so in - C:\Users\Me\AppData\Roaming\Thunderbird\Profiles (so the %APPDATA%\Thunderbird\Profiles\) (Because they are here since the start, many years ago)

No error message at all, even the "The Local Directory path is not suitable for message storage". I have this error if I go in setting, but I just need to close the windows, and nothing happen. The forbidden folder is still used.

But I have my answer, thx for it, so yes it's normal, Thunderbird like create multiple and random folders, it's normal, stupid for me, but it's personnal. And for me easier to forget one of them. And with the "forbiden folder" feature, more issues are possibles.