SPF Engine

This project provides the SPF (Sender Policy Framework) back-end for
both pypolicyd-spf (for which it was originally developed) and an future
SPF milter using pymilter. The goal is to provide a common back-end for
common features for support SPF integration with Postfix and Sendmail
using both the Postfix policy service and the Sendmail milter protocol
(also available with Postfix).
