#!/bin/bash
# Send an email with the status of the SMTP queue on the system.

# Default configuration.
# This can be overridden in /etc/default/warn-smtp-queue.
EMAIL_TO=('sysadmin@slackware.uk')
EMAIL_FROM="\"Server: ${HOSTNAME%%.*}\" <noreply@slackware.uk>"

# Allow /etc/default/warn-smtp-queue to override default configuration.
[[ -e /etc/default/warn-smtp-queue ]] && {
  # shellcheck disable=SC1091
  source /etc/default/warn-smtp-queue || {
    printf "%s: %s\\n" "${0##*/}" "failed reading /etc/default/warn-smtp-queue" >&2
    exit 1
  }
}

# Don't do anything unless 'mailq' is installed.
hash mailq 2>/dev/null && {
  # Prevent a race with other cron jobs that produce emails.
  sleep $(( 10 + (RANDOM % 30) ))

  # Get the queue
  TMP_OUTPUT="$(mailq)"

  [[ -z "$TMP_OUTPUT" ]] && exit 0

  # Send the message.
  if [[ -n "$EMAIL_FROM" ]] && [[ -n "${EMAIL_TO[*]}" ]]; then
    mail -r "$EMAIL_FROM" -s "Mail queue" "${EMAIL_TO[@]}" <<<"$TMP_OUTPUT" >/dev/null 2>&1 || {
      printf "%s: %s\\n" "${0##*/}" "mail command failed" >&2
      exit 1
    }
  else
    printf "%s: %s\\n" "${0##*/}" "no sender and/or recipient configured for mail delivery" >&2
    exit 1
  fi
}

exit 0