Version: (using KDE 4.3.5) Installed from: Ubuntu Packages I can't give any 100% reproducable steps to reproduce this problem, but here on my eeepc it is happening about any other time after I wake up the computer from suspend to RAM. After suspending to RAM (I made sure no dimap sync was running any more!) and waking up again, on the next dimap sync the dimap cache of some random folder (most of the time it is the inbox, but sometimes it is the calendar folder, or some other folder) is invalidated and the whole folder is downloaded again. This is particularly bad as I'm on a prepaid UMTS plan for my eeepc, and downloading the ~500MB inbox takes forever (~2 hours) and it costs me something like 5 or 8€ each time it inbox cache is invalidated. That completely defies the whole purpose of dimap!!!
Thank you for taking the time to file a bug report. KMail2 was released in 2011, and the entire code base went through significant changes. We are currently in the process of porting to Qt5 and KF5. It is unlikely that these bugs are still valid in KMail2. We welcome you to try out KMail 2 with the KDE 4.14 release and give your feedback.