Import Mbox-data to K9

I am using Thunderbird for several years. In this time i have build a complex folderstructure. This i have exported to mbox-file. Now i want to import this to K9 to be able using my folderstructure in an Android App. How is this to realise ?
Thanks much

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You can’t. You can use IMAP with that folder structure on a server.


Hi, linkp.
Thanks for this.
I guessed something like this.
But i won’t be able to create an imap-folder with sub-folder, especially no sub-folder with sub-folder.
My EMail- Provider is “”. On i had the described experience.
I also tried this on “” unsuccesfully.
It seems that only outlook related to exchange- Server is able to create complex folder- structure.
I have converted the mbox- Export of my Thunderbird-folder- structure to pst- Format and imported this to a local outlook- pst- account. It works.

I read about merging K-9 and thunderbird and the intention to create a Thunderbird-App based on K-9. Timedestination was intended at summer 2023.
What’s the matter with ?

I am hopefull to get Thunderbird -App with Functions like a local Thunderbird- Version. Means especially mbox-import.

I have nested folders many levels deep, so I don’t know why you are having trouble with this. This may be an mbox vs maildir difference. I know nothing about your provider. I have always run my own IMAP server.

I wouldn’t expect this from a mobile, app, but who knows, we may be surprised one day.

In the meantime, I would suggest using a desktop application to do the heavy lifting.

It’s already in full swing, see this thread, this and this :wink:

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Hi, linkp.
Thanks for thois inview.
Yes, the own IMAP-Server is really an alternative but I am no specialist in doing like this and have to use offers of IMAP-Server-Provider.
Therefore Thunderbird- Desktop- Solution is a very practicable mailclient.

But may be it is really to much, expecting this from a mobile APP, how you considered.


K-9 Mail was not built as a browser/manager for locally stored emails.

The app requires a server to work. It downloads emails and keeps a local cache of the messages on the server. That gives the app some capability to work offline. Still, changes made while being offline will be synced to the server once the connection is re-established.

The app was never designed to download messages from a server and then exclusively manage them locally. That’s why even when using POP3 there’s no “download, then delete from server” option. That’s also why there’s no option to create local folders. The app currently doesn’t support importing or exporting messages.
All of this might change in the future. But it’s not something that is currently on the roadmap.

You can use Thunderbird on desktop to copy or move all of your local messages to an IMAP server. The Android app will then happily download and display those messages and folders. Changes made using one email client are synced to the server and will subsequently be visible to other clients.


Be greeted, Cketti.
Thanks for this detailed und clear answer.

So like linkp handle it with his own IMAP- Server, I cant do.
My Mail- Provider doesn’t support nested folder- structure.
So i would only be able to create a lot of single folder manual as alternative to my nested structure. A lot of work.

I found out, that gmail is able to create nested folder. So i have to decide transfering my Mail-archive in Thunderbird to gmail.

Thanks a lot for this suggestions and trigger.


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