Build the binary like described in README.build.

Copy sigh-example.cfg and mapfile-example.txt and rename them. Make changes to
these files. The example files are well documented.

Start the milter i.e.:

./sigh --debug --config /path/to/your/modified/config

See full list of options with:

./sigh -h

The funny name of the milter is baed on an idea from Patrick Ben Koetter.