examples/test trains dictionaries on read and junk mail between 100 and
800 days old, then reports classification statistics for read and junk
mail less than 100 days old. For my mail at the time of writing, this
yields a training set of around 10k read messages and 50k junk messages,
with a test set of around 1k read messages and 10k junk messages.

examples/whitelist/generate creates a whitelist using the From: headers
of read mail less than 800 days old, filtering out my own addresses as
spam is often sent with a From: address to match the recipient.

examples/whitelist/deliver demonstrates how this automatically generated
whitelist can be integrated into a delivery filter.