dgrey is a greylisting policy server that allows
greylist information to be synchronized between
multiple mail servers. All information is shared
between the nodes and the nodes are equal; there
is no master. The nodes may lose communication for
a while and still be able to correctly
resynchronize later. This works because all nodes
keep a log of changes to the database. All
communication is done across TCP connections,
which can optionally be password protected. dgrey
works with mail transfer agents such as Postfix
and Exim.
