Using DBMail with Exim4 by Thomas Mueller
Every router with local mail has to use 'transport = LOCAL_DELIVERY' then.
# transport using pipe transport_dbmail: driver = pipe command = "/usr/local/sbin/dbmail-smtp -d $local_part@$domain" return_fail_output user = dbmail
# transport using lmtp; exim and dbmail on the same host transport_dbmail: driver = smtp protocol = lmtp hosts = localhost allow_localhost return_path_add
LMTP requires lmtp entries in /etc/services (they are not there in Debian!).
lmtp 24/tcp lmtp 24/udp