[Unit]
Description=msmtp daemon
Documentation=man:msmtpd(1)

[Service]
DynamicUser=true
AmbientCapabilities=CAP_NET_BIND_SERVICE
CapabilityBoundingSet=CAP_NET_BIND_SERVICE
NoNewPrivileges=true
# NoNewPrivileges prevents the setgid mechanism from working
# so since msmtp is setgid in order to read /etc/msmtprc, the
# msmtp group need to be added in a different way
SupplementaryGroups=msmtp

Environment=INTERFACE=127.0.0.1 PORT=25
EnvironmentFile=-/etc/default/msmtpd

Type=simple
ExecStart=/usr/bin/msmtpd --interface=${INTERFACE} --port=${PORT}

Restart=always
RestartSec=60

ProtectHome=true
PrivateTmp=true

[Install]
WantedBy=multi-user.target