/lib/systemd/system/mail-transport-agent.target is in systemd 215-17+deb8u7.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 | # This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
# This exists mostly for compatibility with SysV/LSB units
# depending on the $mail-transport-agent system facility.
[Unit]
Description=Mail Transport Agent
RefuseManualStart=yes
|