Every time I add a filter with Tools > Message Filter, the filter appears in the Thunderbird menu but not in the underlying msgFilterRules.dat file. When I restart Thunderbird, the filter is also gone from the Thunderbird menu (not in Thunderbird menu anymore, and still not in the underlying msgFilterRules.dat). (I am using a symbolic link to a msgFilterRules.dat file in a folder that I sync with another computer, but that doesn't seem to be the problem; when I stop doing that, and use a "normal, fixed, local" msgFilterRules file, the problem persists). Anyone any idea what could cause this behaviour? Thanks a lot!