You control that at the 'copies&folders' pane of the account. After archiving, you can then check the online account to verify that it is not there.

Define archived and then we can talk. Seriously. if you are downloading mail using Thunderbird with the IMAP protocol you are not making something that could be considered a long term archive in any way shape or form. The sever is considered canonical in the IMAP protocol so our local copy is only as good as the server one.

Using POP will generally download an immutable copy of mail in the inbox. But no other folders. It will also not remove mail from the server by default. You have to manually set that in account settings.

You could also copy mails into the "Local Folders" special account as that is truly a local store with no links to the server. But after you verify the copy. You still need to delete the emails. It is possible move will work for you, but the more mail being processed the higher the risk of mail simply not moving.

Mostly I see folk with an unsatisfactory archive arrangement with their hosting provider trying to bend local mail clients into archival tools they were never intended to be. They can perform that function, but it is not natural for them and considerable oversight is usually required fro when issues occur.

Some folk use filters to move mail from IMAP folders to local folders storage with varying levels of success. Basically it is another instance of trying to bend the tool to the function rather than use an archiving tool. Some will tell you it works like a charm. Others will say it has problems and et others will say it has lots of problems don't touch it. One thing is apparent, the larger your individual emails the higher the risk that the filters will timeout while in processing the mail and will not be removed, will be copied multiple times or just plain lost from the server or other anomalous issues surface. There is no real automated guaranteed solution.

The best solution is to archive on the server and periodically make backup of the contents of the archived folders in Thunderbird using the importexport tool and then delete the mails from the archive folders. https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/?src=ss

I recommend mbox backup files that you name for the time they represent say June2025 and july2025. That way you can use the same tool to reimport the files into Thunderbird local folders should you want to access the mail in a mail client without any issues at all.

Thanks Matt. I'm new to Thunderbird. My e-mail access has been via CPanel and Roundcube on a GoDaddy hosted domain. Their archiving possibilities are limited and each e-mail address has a limited space allocation, so I want to archive old messages outside that allocation. Yes I use IMAP and access e-mail on different devices, but will be happy if I can persuade Thunderbird to move (or at least copy) them on to the drive of my main Windows 11 computer. I.e. actually create files on he computer. So that they are (or can be) removed from the server.

But so far specifying 'Local copy' in Thunderbird has only managed to expand my CPanel directory structure to:

Inbox

  Archive 2022
  Archive 2023

and the 'archived' messages still count against my allocation. I am lacking a 'mental model' of what Thunderbird is doing and it appears I have misunderstood something.

My Thunderbird account settings tell me that my Local folders are at

,,,\AppData\Roaming\Thunderbird\Profiles\pytp1ii4.default-release\Mail\Local Folders

but pressing the Archive button doesn't seem to be putting anything there.

So on the one hand it looks like I should be able to persuade Thunderbird to move (or copy) stuff there, but on the other, from what you say, it looks like I should be exploring the import/export add-on.

Dave

To follow on Matt's direction, here are possible steps to take:

1. first, install the account as IMAP. You can specify this during setup
2. then, create the online archive folders per Matt's suggestion and populate as desired
3. then, click the 'synchronization&storage' pane and the 'advanced' button to verify that all desired folders are set for download
4. while on that pane, check that disk space is set to sync all messages
5. next, click file>offline>download to ensure all messages are downloaded (if menu bar not visible, press the alt key first)
6. at this point, all messages should be on PC.
7. install the addon, importexporttools NG
8. highlight one of the newly-created archive folders, rightclick, and select the importexport option to export mbox
9. repeat the step for other desired folders
10. now, highlight Local Folders
11. rightclick and select the importexport option to import mbox and select one of the exported mbox files
12. repeat for the remaining folders - spot check to ensure you can view content on each folder
13. at this milestone, you have safely copied all messages to Local folders
14. then, per Matt's instructions, you can delete the contents of those archive folders you populate back in step2.

Thanks David for the step-by-step instructions. I'll give it a go.