I've been using Kmail for over 10 years, most recently with kubuntu 10.04. I've now upgraded to kubuntu 12.04 which went very well except for kmail which is broken.

Initially I was able (using "kmail-migrator --interactive" after the initial migration failed) to get a working kmail which did have my old folders, and did send and receive mail. But warnings were continually popping up, on nearly every message received or my reading different messages. These included:
"Resource Kmail Folders is broken. This resource is now online"
"Kmail Folders: Error while reading mails from folder"
"Kmail Folders: Cannot modify emails in folder"
"Kmail Folders: Cannot move email from folder"
"Kmail Folders: /home/... does not seem to be a valid email folder"
I emphasize that these error message appeared even when the action, such as a move, was apparently completed successfuly. And Kmail _was_ generally working successfully so far as I could see - except for the error messages!

Anyway I decided to start from scratch and so far as I can tell have removed and started from scratch, removing files at
~/.kde/share/config/kmail*
~/.kde/share/config/akonadi*
~/local/share/akonadi*
~/config/akonadi*
then starting akonadi and kmail.

Akondai appears to be configured, showing 3 resources marked "ready"
Local Folders
Notes
akonadi_pop3_resource_0

Kmail shows an apparently clean setup, a "Local folders" directory under which are "inbox", "outbox" and "sent-mail". I can receive email on it. However,
() there is no "trash" folder - if I send a received message to "trash" it simply disappears
() sending a mail is unsuccessful - without any warning/error message (and I've replaced and checked the smtp account setting several times to make sure it is correct) - the message just ends up in "outbox" under "Local folders" where it sits, even when I click "send queued messages"

So after working for over a full day on this I'm ready to move on to some other email program, as so many seem to be doing with the advent of kmail2. I have gotten evolution to work successfully with my old folders (though must re-create my filters). Still, I'd like to give kmail one final chance to work correctly, since I have enjoyed using it for so long - hence my post here. Lord knows from googling I've read many post with advice about kmail2 failures and have tried to learn and follow from them, but at this point I can't find anything in them which seems helpful.

Did you try the following:

- Can you upgrade to KDE PIM 4.10 (should be available as an extra repo for 12.04)? It brings many improvements
- Remove the POP3 resource, and readd it fresh;
- Add a trash folder to the local folder (I believe there was a bug regarding that, but it's now fixed, IIRC)
- Ensure that in "akonadiconsole" you see a "mail delivery agent" and that's listed in "Online" state.

() I have now upgraded to kubuntu-12.10 (which produced its own problems including a trashing of my grub2 setup, which I have just now recovered from - the upgrade to 12.04 did not have that problem)
I assume that 12.10 has the PIM4 you mention as I don't know how to check for that
() Running akondiconsole finds a "Mail Dispatch Agent - ready to dispatch messages"
() I added directories trash, trash/cur, trash/new, trash/tmp to ~/.local/share/local-mail
(which produced warning messages ala "Mail Dispatch Agent: could not access the outbox folder file (failed to fetch the resource collection)"
() I'm unsure whether your reference to the pop3 resource refers to the "akondi_pop3_resource_0" I see in the akondiconsole or to account setting in Kmail. So I tried to at least change the latter, but now starting kmail produces error message "Email program encountered a fatal error and will terminate now - The error was: failed to fetch the resource collection). FWIW evolution still works.

Update: stopping & restarting akonadi seemst to have corrected the Kmail startup failure problem. There is now a "trash" directory". Will now replace the pop3 account setup in Kmail.

() In Kmail "Accounts" config, I deleted and readded "Sending" & "Receiving" under "akondi_pop3_resource_0" - which had the effect of changing its name to "POP3 Account".
() I then sent a new message to myself (at external server) and that was successfully sent & received - and moved to "trash" afterward.
When composing the very first new email to send, a message "You do not have the semantic desktop enabled. The following functions will not work correctly ..." appeared in the composer box. But that did not occur for the second test message I composed and sent and received.

So it appears I now have a working bare account, thanks to your help.

But now I must try to add my old maildirs. The current situation is that my "local folders" are at ~.local/share/local-mail/. I have a old maildir directory (which was ~/Mail but for the clean setup I changed its name so it would not be found). What is the best (i.e. most likely to succeed) way of incorporating that old maildir directory into my current setup?

Uh oh - I've encountered problems when adding my local /var/spool/mail mbox (so I can receive email messages sent by local programs which run on my computer). In the past that has not been a problem with Kmail. But now setting up a new mbox account, with "mbox locking off" (default) I get errors ala "The Mbox file was changed by another program. A copy of the new file was made and pending changes are appended to that copy. To prevent this from happinging use locking and make sure all programs accessing the mbox using the same locking" [Message A] . ALSO, "The file ../var/spool/mail/,, was changed on disk. As a precatuion, a backup of its previous contents has been created at file..." [Message B].

So I tried setting the Accounts Resourse mbox locking to "mutt dotlock", exiting Kmail, deleting the mbox (/var/spool/mail) file itself, then sending a message via mutt. But on re-starting Kmail, I get messages ala "Failed to read message with old "...var/spool/mail/..." [Message C]. And while a message appears in the mbox I cannot move it.

So I tried setting the Accounts Resourse mbox locking to "mutt dotlock previledged", exiting Kmail, again deleting the mbox, then sending a message via mutt. Then on re-starting Kmail there are no error messages - , but there is nothing showing in the mbox (even though there is definitely one in the mbox file itself).

Unless I can get Kmail to work with my local /var/spool/mail mbox, with my mail programs being able to send mail to it as they have been doing, Kmail is worthless to me. (And yes, I have tested evolution and found it is able to have messages sent to a local mbox without any problems.)

There are known issues with local mailboxes, IIRC.

OK, thanks for your time. My computer has to be a tool, not a toy, since I create and run programs/tools for my websites on it, and I do require that my email program be robust - so will be moving on. Personally I feel that the Kmail/KDE developers have failed a trust that I had placed in them so I do not want to be dependent upon them in the future.

[My background: from IBM-PC-XT in 1985 (with email) to Unix SGI/Sun workstations to Linux after Unix died. I do miss the Unix days when things always worked. I now have scads of self-installed programs on my linux machine which would be very time consuming (and frustrating) to start from a clean install, so will continue to go the ubuntu update route as long as I can. But I've vowed that if I ever have to start from a clean install I will switch to a RedHat desktop and pay for their support, just as I pay for RedHat on my web server. Ubuntu/kubuntu is "free" only if one's time is not very valuable.]