This directory contains the "penaltybox" and related programs.  These are
meant to be invoked from the simta content filter.  

The penaltybox program communicates with an external database to
store and query message checksums. It uses these database records to
implement a form of mail greylisting for mail inbound to a domain.

Also included is the "userthrottle" program. It uses a similar scheme
to monitor per-authenticated-user mail sending rates for a domain, and
optionally manage the same.