Fake SMTP server to relay any message to a specific mail account via a specific MTA.
$ perl resmtp.pl \
[-d|--daemon] \
[-h|--host <listen_host>] \
[-p|--port <listen_port>] \
[-t|--timeout <timeout_in_seconds>] \
[-b|--blackhole] \
[-f|--from <smtp.mail.from@example.net>] \
<recipient@example.net>[,<recipient2@example.net>,[...]] [<smtp_host[:port]>]
# cat <<'EOF' > /usr/lib/systemd/system/resmtp.service
[Unit]
Description=resmtp Service
After=network.target
[Service]
Type=simple
ExecStart=/usr/local/bin/resmtp.pl --host 127.0.0.1 --port 25 recipient@example.net
Restart=on-abort
[Install]
WantedBy=multi-user.target
EOF
# systemctl enable resmtp
# systemctl start resmtp