The dk-milter package is an open source implementation of the DomainKeys
sender authentication system proposed by Yahoo!, Inc.  It consists of a
library that implements the DomainKeys service, and a milter-based filter
application that can plug in to the sendmail MTA to provide that service
to sufficiently recent sendmail MTAs.

An optional asynchronous resolver library is also provided to work around
limitations of the basic BIND resolver which comes installed on most
systems.