Version:           1.13.1 (using 4.4.1 (KDE 4.4.1), Debian packages)
Compiler:          cc
OS:                Linux (i686) release 2.6.32-3-686

Since my upgrade from KDE 4.3.4 to 4.4.1 and the respective versions of KMail, I'm having trouble with messages not being properly deleted from the POP3 server. As a result, the affected messages are retrieved from the server again and again on each periodic mail check. This only stops when I delete these messages from the server by some other means. KMail is configured to immediately delete fetched messages from the server.

It is not the case that no messages are deleted from the server. Things work correctly for a period, then suddenly, messages are not deleted properly anymore and in turn are retrieved endlessly. A way to provoke this behavior is to suspend the computer and later resume it.

As far as I can tell, enabling or disabling pipelining doesn't have an effect; the server reports that is supports pipelining. Normally, I'm using SSL, but with it switched off, I noticed that apparently KMail does send DELE messages, however they are ineffectual. I've only been able to observe anything after things already were broken. I've not been able to observe the breaking itself.

This might all sound like the POP3 server is at fault. However, it is a widely-used server at my ISP, other users I know of don't have similar problems -- and my trouble started exactly when I updated to KDE 4.4.1.