Kmail messages broken: “no subject” and “sender unknown”

[JohanLingen]

System:
Kubuntu Feisty, Kmail (embedded in Kontact).

Symptoms:
A few days ago, my complete inbox broke down: I receive empty messages for each new email on all my accounts (in subfolders of the inbox), showing “no subject” and “sender unknown).

Possible cause:
I think the problem was born after I tried to synchronize my personal files (among which is the kmail/mail dir) with another computer, using the application Unison (pity it wasn’t finished yet).
I use the mbox format (because I could not migrate maildirs to a fresh installation, see http://kubuntuforums.net/forums/inde...opic=3080767.0).

Actions:
I removed the *index* files of the inbox and the subfolders, but the problem persists. Also, it did not have any effect to remove the config files from ~/.kde/share/apps/kmail/config (kmailrc and …)

How can I fix this and how can I prevent it from happening again?

[JohanLingen]

Re: Kmail messages broken: “no subject” and “sender unknown”

Eventually, I backed up the mbox files, added new folders in kmail and imported messages from the old mbox-files. Even the messages marked by "no subject" and "sender unknown" became readable.