Switching directories from maildir to mbox in kmail 4.14.1

[Martin Steigerwald]

rhkramer at gmail.com - 19.05.19, 03:47:
> On Saturday, May 18, 2019 09:18:57 PM rhkramer at gmail.com wrote:
> > Background: For a period of time, I have to do some work on a Debian
> > Jessie system.  The supported version of kmail is 4.14.1.  I've

An ancient version of KMail.

> > discovered that, by default, mail folders are set up as maildir.
> > 
> > I need to switch them bo mbox -- how do I do that?

Why would you need to switch them to mbox? Maybe there is another 
solution to the goal you like to accomplish.

> I should add that I've done some googling, and found some instructions
> that seem to imply the when I create a new folder, I should get a
> popup that has a selection for mbox or maildir.  That doesn't popup
> on this system.

There are three resources for local mail storage:

1. Maildir (default): stores mails in a maildir folder structure.

2. Mbox: Accesses a single mailbox file (good for local mail in '/var/
spool/mail').

3. Mixedmaildir: allows to decide per folder whether to use maildir or 
mbox.

I bet the third would show up the popup you mentioned. However it has 
been a long time I last used it.

When you create a new user defined resource for receiving (and storing) 
mails I believe when you use 'KMail mail folder' (roughly translated 
from German) you will get mixedmaildir resource.

Please note tough: I migrated away since back then KDEPIM developers 
changed the default as well and wrote several times that they do not 
recommend using it anymore. It has a completely different implementation 
and since it is not the default anymore, it likely does not receive as 
much testing as before.

In general it should work, but on attempts to import a KMail mail folder 
resource folder into KDEPIM some years ago I saw a very high memory 
usage. I stopped the import which I triggered by creating a KMail mail 
resource pointing to that old folder due to intense swapping¹. It has 
been a long time ago and this issue may be fixed meanwhile. However you 
are using an ancient version of KMail and  I believe mixedmaildir 
resource did not receive much development work for a long time – so the 
bug may still be there. (Don't bother to reopen the bug report when it 
is still there in such an ancient version of KMail tough.)

The folder I tried to import contained only MBox folders I used for 
archival. Prior to removing the mixedmaildir resource before migrating 
to a newer version of KDEPIM/Akonadi back then, I created a new pure 
maildir resource and separated migrated all maildir folders to it so 
that the old mixedmail resource just contained mbox folders anymore.

I'd actually like to use the mixedmaildir thing again cause a folder of 
mbox folders is really nice to archive mails and still have them 
accessible within KMail. Cause rsync'ing a few mbox files that do not 
even change afterwards anymore to backup disk is much faster than 
rsync'ing millions of little mail files. For now I just tar maildir 
folders with huge mailing lists and then remove them afterwards from 
time to time to keep Akonadi performance above a certain level. At one 
point when computers and Akonadi have more performance I may re-import 
them by just un-tar-ing them into the right location within the maildir 
resource folder.

So or so I believe for KDEPIM/Akonadi developers there is more important 
work to do than to deal with any issues mixedmaildir resource may have.


[Akonadi] [Bug 334318] New: on adding old mail archive mixedmaildir 
resource consumes tons of memory
https://bugs.kde.org/show_bug.cgi?id=334318

Thanks,
-- 
Martin