Version: 4.2.96 (using KDE 4.2.96) OS: Linux Installed from: Fedora RPMs Kmail provides spam filtering. In Filter Rules configuration - advanced options: check box "Apply this filter to incoming messages simply does not work for imap accounts that have messages filtered to folders on server side. It seems check box means only "apply this filter to new messages in inbox". New messages in inbox are spam filtered. New messages in other folders are not spam filtered. Spam filtering works only for inbox folder and there is no way how to create new filter rules for other folders.
*** This bug has been marked as a duplicate of bug 100786 ***