It was working fine for me, but after the last update it crashed mail whenever I try and launch the program, it starts to check, but as soon as it calls SpamSieve it crashed. I had to remove the bundle to get it to work.
According to the crash log, the SpamSieve plug-in wasn’t doing anything during the crash. It looks like Mail crashed while evaluating some rules with address book criteria and while parsing some HTML. Have you tried restarting your Mac? What happens if you install the SpamSieve plug-in but uncheck the SpamSieve rule?
Just happen again. The exact same thing. And the fix is to uninstall the Spam Sieve Bundle, and let Mail open, then deal with all the mail it marked as Spam. And then re-install Spam Sieve and restart mail, and the problem seems fixed, for a while at least.