/etc/exim.routers.pre.conf

exim.routers.pre.conf

mv /etc/exim.routers.pre.conf /etc/exim.routers.pre.conf_BUG
echo 'lookuphost:
  driver = dnslookup
  domains = ! +local_domains
  ignore_target_hosts = 127.0.0.0/8
  condition = "${perl{check_limits}}"
  transport = remote_smtp
  no_more' > /etc/exim.routers.pre.conf

service exim reload

cp -f /etc/exim.routers.pre.conf_BUG /etc/exim.routers.pre.conf
service exim restart


# https://p5r.uk/blog/2017/smtp-via-ssh-tunnel.html
ssh-keygen -t ed25519 -f /root/.ssh/smtp_tunnel
ssh-copy-id -i /root/.ssh/smtp_tunnel user@mx.example.com
command="nc localhost 25",no-X11-forwarding,no-agent-forwarding,no-port-forwarding ssh-ed25519 AAAAC3Nz…
/etc/systemd/system/smtp-submission.socket
[Unit]
Description=SSH Tunnel to mx.example.com for SMTP submissions

[Socket]
ListenStream=25
Accept=yes

[Install]
WantedBy=sockets.target


-----
/etc/systemd/system/smtp-submission@.service
[Unit]
Description=SSH Tunnel to mx.example.com for SMTP submissions

[Service]
ExecStart=-/usr/bin/ssh -q -T -i /root/.ssh/tunnel_key user@mx.example.com
StandardInput=socket
------


systemctl enable smtp-submission.socket
systemctl start smtp-submission.socket
systemctl status smtp-submission.socket


systemctl enable smtp2-submission.socket
systemctl start smtp2-submission.socket
systemctl status smtp2-submission.socket