Watchdog fails to send email if first MX record is down

[ScrumpyJack]

This one is a bit long winded, so apologies for the editing mess.

watchdog.sh starts up and resolves MX with dig +short ${RCPT_DOMAIN} mx

If dig returns an mx record, it then sends an email with smtp-cli

smtp-cli then looks up MX records as well with Net::DNS::mx and always returns the first element of the array which is the first MX record in the order of priority (so it will always return the same MX record)

If that mx is down, you'll never get emails as smtp-cli does not try another mx record.

smtp-cli is unmaintained, so it might be better to fix it in watchdog.sh by checking each $mx returned by dig (in MX priority order) using smtp-cli --server $mx, then when the first that responds is found, pass it to smtp-cli --host