MacMail Crashes Every Time I Create a Rule for an Auto Responder

Please assist me.

Every time I create an Autoresponder on my mac mail, it begins to crash. Then when it reopens it crashes and crashes and crashes.

I end up having to go into the library folder > Mail > Rules Active File and have to delete it.

Can someone shed some light as to why this happens and how I can resolve this?

Thanks

L