This delivery plugin provides a shortcut for delivering messages between two
domains that are running on the same server. It also allows inter-VHost
communication on hosts that do not have S2S enabled at all, enabling admins
to create a closed pool of vhosts on one server that can only talk to one another,
if configuring S2S is impossible or inconvenient.
This plugin wont do anything at all unless you allow at least one vhost as
shown in the example above. By explicitly listing the appropriate services
you can create segregated pools of vhosts that cant communicate between
each other but can communicate within the configured bounds.
TODO: more docs