Version:            (using KDE 4.3.5)
Installed from:    Ubuntu Packages

It has happened three times during the past year that KMail almost completely cleared either the INBOX (once) or the calendar folder (twice). Unfortunately, I cannot give any concrete steps, just some observations that might help finding the area of the problem:

-) I'm running three computers (office PC, home laptop, eeepc), with all three running kmail and auto mailcheck at all times.
-) The problem happens only on the eeepc, which is the only computer where I user suspend to RAM (while kmail is running). In all cases where a folder was almost cleared, I had used the eeepc shortly before (and the message removal probably happened then).
-) In all cases, the folder was not entirely cleared, but some messages were left in the folder. These were newer messages, while all the old messages were removed from the inbox / the calendar folder. Most of the remaining messages/events were created/received less than a week before the incident happened, but some older are also preserved (although none older thatn 6.5 weeks is preserved).
-) It is not the same problem as bug #230699, since old/existing mails are deleted from the server, too.

Unfortunately, these are all my observations. I'm sorry I don't have any more details on the problem, but it appears randomly and only seldom, so it's hard to track.

Unfortunately, such data loss is about the worst that can happen (I had several appointments for vocal auditions including all contact information in my calendar, when kmail decided to almost clear my calendar folder... It doesn't look too professional that I have to call them -- if I can get their phone numbers again, that is -- and ask again about the details!)

Currently, the only thing that is keeping me with KMail is that KOrganizer is the only calendar application that can print out beautify weekly timetables (and since I'm using three computers, I need a groupware solution, so dimap over KMail is required.)