I have a screen shot of what the failure is showing, as well as what
the
error is itself after clicking on it.
http://www.miketc.net/junk.png
The only thing it doesn't show is the tab in the bottom left that says
"Check Junk failed". But I clicked on it and that gave the error
message in the middle of the screen about not piping to bogofilter or
something.
Try to run evolution from console and look there whether there are more
warnings. There can be.
I looked on this page:
http://www.bogofilter.org/man_page.shtml
and in the section "Return values" is described, what that can return.
They have used the 3 for some error. The bad thing is that Evolution can
fallback to the code 3 itself, when something wrong happened when
waiting for process end (call to 'waitpid'). In that case there should
be some warnings on the console.
Bye,
Milan