Version: 1.9.1 (using KDE KDE 3.5.2) Installed from: Gentoo Packages Compiler: gcc 3.4.6 OS: Linux I have an online IMAP account that kmail displays as threads in the message list. If I select a particular message in a thread and apply a filter to it, the filter is (successfully) applied but the thread is then closed in the message list and I have to click the "+" sign to open it again. I would expect the thread to stay as it was before applying the filter, i.e. open if it was open. Note, I discovered this when using the spam handling filters but it happens with all my other filters too.
Confirmed in KDE 4.3
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.