Version: 1.9.10 (using 3.5.10, Gentoo) Compiler: Target: i686-pc-linux-gnu OS: Linux (i686) release 2.6.27-gentoo-r8 Currently it is possible to define a filter w/o an action.
I can confirm this on kmail 1.11.0, although it doesn't really hurt. It's just a filter that does nothing. Thus, I change severity to minor.
I've submitted a patch to reviewboard.kde.org which causes kmail to complain if a filter doesn't have a matching pattern, actions or accounts.
Actually, a filter without filter action can be used as stop filter, i.e. to stop processing of the following filters if certain criteria are met. One use case is disabling filtering temporarily by adding such a stop filter as first filter. Resolving as WONTFIX.