Add option to automatically reject message

[coderforlife]

Just like there is a percentage cutoff for what to mark as spam, another option should be available to simply reject messages about a particular cutoff. I get numerous 99% messages a day, I would set it to probably 90% or 95%. Then between 70% and 90% should be kept but marked as spam. Over time I may adjust those (say I never get anything legitimate about 80%).