Adds a basic mail monitoring.

unit-files/mail-mon.service

+[Service]
+Type=oneshot
+ExecStart=/libre.sh/utils/mail-mon.sh

unit-files/mail-mon.timer

+[Unit]
+Description=Run mail mon hourly and on boot
+
+[Timer]
+OnBootSec=15min
+OnUnitActiveSec=1h
+
+[Install]
+WantedBy=timers.target

utils/mail-mon.sh

+#!/bin/bash -eux
+
+/usr/bin/journalctl --since '1 hour ago' | grep postfix/cleanup | grep "from=" | sed -n 's/.*from=<\(.*\)> to=<\(.*\)> pro.*/\1/p' | sort |uniq -c | sort | awk 'BEGIN {FS=" ";} {printf "mail_sent{domain_name=\"%s\"} %s\n", $2, $1}' > /system/metrics-collection/textfiles/mail.prom