/etc/systemd/system/multi-user.target.wants
Edit: /usr/lib/systemd/system/postfix.service (282B)
[Unit]
Description=Postfix Mail Transport Agent
Documentation=man:postfix(1)
Conflicts=sendmail.service exim4.service
ConditionPathExists=/etc/postfix/main.cf
[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/bin/true
ExecReload=/bin/true
[Install]
WantedBy=multi-user.target