The "account" kmail folders shows all folders that exist in ~/Mail. However if I click on a folder no content is shown. Looking at akonadi's output I see a lot of activity regarding that resource and the following debug output. KMail1 can display the emails just fine thus I do not think it is a permissions issue.
akonadi_mixedmaildir_resource_0(16165)/akonadiresource (maildir): "Cannot add email to folder because there is no email content"
akonadi_mixedmaildir_resource_0(16165): "Given folder name is empty"
akonadi_mixedmaildir_resource_0(16165): Collection ID: 86 remote ID: ""
parent: -133645 ""
contents mime type: ()
sync on demand: false
local parts: ()
unread count: -1
size: -1 Item(remoteId= "" , mimeType= "message/rfc822" )
Reproducible: Didn't try
right clicking and "synchronise folder" does help for some but not for others.
Synchronise folder did not help for me either. My trash folder still says 900 messages, 437 unread, but no content, KMail 2.1.0 shows an empty folder.
You can check with akonadiconsole wheter it's kmail or akonadi.
I have the same problem. I've found out the messages (as text files) in ./kde/share/apps/kmail/mail/.index.directory/../new aren't corrupted, just it is unable to open them in kmail :-(
This bug has only been reported for versions older than KDEPIM 4.14 (at most akonadi-1.3). Can anyone tell if this bug still present?
If noone confirms this bug for a recent version of akonadi (part of KDE Applications 15.08 or later), it gets closed in about three months.
Just as announced in my last comment, I close this bug. If you encounter it again in a recent version (at least 5.0 aka 15.08), please open a new one unless it already exists. Thank you for all your input.