RFC 6647 graylisting policy server, following the recommended practice
noted in the standard document.
Graylisting defers message acceptance (for a specific recipient / sender
/ client_address value tuple) a configurable number of times
via a standardized SMTP response (see allow(5), RFC 5321), which does
not prevent message delivery from SMTP M(ail) T(ransfer) A(gent)s,
but can help against simple spam producing programs.
s-postgray is started via spawn(8), with the given user credentials,
therefore the built-in DB store path is /tmp -- you surely want to
change this via configuration file or command line option.
from Steffen Nurpmeso (maintainer and upstream), with tweaks from sthen@
and me. ok sthen@.
