Comment 3 for bug 819676

I have a similar problem (on 11.04, KDE updated through the backport PPA). It also devoured my emails. When I turned on the spam/anti-virus filters, it deleted them from the IMAP server (my email provider is GMX), ran the checks, then tried to upload them back to the server and I got a similar message; "could not upload the message ..." "unexpected end of data." The net result was that the email was deleted, and was not present either on my computer or the server. I lost a few days of emails, until I found a work-around (firstly using thunderbird to read email, then switching off the spam/anti-virus filters on kmail).

dpkg -l | grep kdepim
ii kdepim 4:4.4.10-0ubuntu4 Personal Information Management apps from the official KDE release
ii kdepim-groupware 4:4.4.10-0ubuntu4 KDE PIM Groupware plugins
ii kdepim-kresources 4:4.4.10-0ubuntu4 KDE PIM resource plugins
ii kdepim-runtime 4:4.4.10-0ubuntu2 Runtime components for akonadi-kde
ii kdepim-strigi-plugins 4:4.4.10-0ubuntu4 PIM file format plugins for Strigi Desktop Search
ii kdepim-wizards 4:4.4.10-0ubuntu4 KDE server configuration wizards
ii kdepimlibs-kio-plugins 4:4.7.0-0ubuntu1~natty1~ppa1 kio slaves used by KDE PIM applications
ii libkdepim4 4:4.4.10-0ubuntu4 KDE PIM library