SPF sender authentication systems.
Sender-ID and SPF have both been published by the IETF (RFC4406 and RFC4408,
respectively) as experimental proposals.
This package consists of a library that implements the record parsers needed
to provide the authentication service, and a milter-based filter application
that can plug in to the sendmail MTA to provide that service to sufficiently
recent sendmail and postfix MTAs.
An optional asynchronous resolver library is also provided to work around
limitations of the basic BIND resolver which comes installed on most
systems.
