WARNING: ifile is no longer being actively developed.
Long, long ago, in a lab far, far away, I used the following to described ifile:
ifile is a general mail filtering system that works with a mail client to intelligently filter mail according to the way the user tends to organize mail. ifile uses the modern machine learning algorithm naive Bayes to classify mail documents.
ifile is different from other mail filtering programs in three major ways:
Now, it can be described simply as one of many "Bayesian mail filters." Though, unlike bogofilter and spamassassin, it can do n-way filtering rather than simply spam vs. non-spam.
There is no longer an ifile mailing list, but you can see the archives.