Hi Rick,

there is a way to choose the maildir format for Local Folders via a manipulation in the prefs.js file but this will not transform messages already stored in the mailbox format into the maildir format. You would first have to export in the *.eml format all messages stored in Local Folders, to import them back in Local Folders once the manipulation in prefs.js file accomplished.

Are you still interested?

In the meantime I've found a much easier way for the conversion from mailbox to maildir format. Go to Settings > General > Config editor... Search for the setting "mail.store_conversion_enabled" and toggle its value from false to true. Now go to Account Settings > Local Folders > Message Store > Message Store Type and select "File per message (maildir)". Your choice made TB will ask you to restart. When you go to the profile folder > Mail you'll see a new folder called "Local Folders-maildir" containing the converted files.

Hi Mapenzi,

Many thanks for your help!

I read that changing the format for local folders was experimental six years ago and had the potential for data loss. It is still not fully enabled in Thunderbird. Do you know how safe it is now?

Rick

I guess you already read this article https://wiki.mozilla.org/Thunderbird/Maildir When you change the format for your Local Folders to maildir, TB will still keep the old Local Folders with the messages in mailbox format.

I've been playing. What I have learned:

Changing mail.store_conversion_enabled and the setting for storage format for local folders seemed to work fine. Thunderbird converted many folders automatically, created a separate "local folders" folder for EML messages, and the results looked good, other than Thunderbird not knowing that all messages had already been read, which is a common problem with importing.

Then I noticed that ImportExportTools NG cannot import (while converting) mbox files into maildir/eml folders. That's a problem. I need mbox files for 1) long-term storage of mail outside Thunderbird, and 2) possible import back into Apple Mail someday. I concluded a while ago that maildir/eml is not a good interchange format, at least on the Mac or at least with Apple Mail. So using this method would require me to convert scores of e-mail folders to maildir/eml now, which I would prefer not to do.

Unless you or someone else knows of a way other than ImportExportTools NG to import mbox files into maildir/eml folders?

This is a meta bug against all maildir like bugs should be recorded as a blocker or depending on it. So anything that is not struck through is still an open bug. It is up to you to make your own decisions. THat was why I actually wrote the original support document and offered the warning. IO was trying to get folk to at least try it and file bugs. Why is in not finished? I have no idea, it languished after the demise of Mozilla Messaging around 10 years ago and the current crop at Mzla have found other new shiny things to capture their interest is my guess, like introducing yet another language into the code base.

https://bugzilla.mozilla.org/show_bug.cgi?id=845952

Thanks for the link, Matt.

How much has changed in the almost six years since you wrote the support article?

Do you believe that the maildir implementation for IMAP folders is stable and reliable enough for use?

I'm getting the impression that it may be, but that the maildir implementation for local folders is less stable and reliable. Is my perception accurate?

Thanks for your help.

Correct link for the support document: https://support.mozilla.org/en-US/kb/maildir-thunderbird