OpenDMARC provides an open source library that implements the DMARC verification service plus a milter-based filter application that can plug in to any milter-aware MTA, including sendmail, Postfix, or any other MTA that supports the milter protocol. The DMARC sender authentication system is still a draft standard, working towards RFC status. The database schema required for some functions is provided in /usr/share/opendmarc/db. The rddmarc tools are provided in /usr/share/opendmarc/contrib/rddmarc.