Bayesian techniques are neither AI nor new. See <http://citeseer.nj.nec.com/sahami98bayesian.html> and <http://citeseer.nj.nec.com/androutsopoulos00learning.html>, among others.
Moreover, while there may be client-side programs which implement these techniques, and there may be prototype server-side programs which implement these techniques, I am not aware of any more production-oriented tools which are available to implement these kinds of techniques.