  
{#
  This health check ensures the test email is sent only once to prevent
  hitting SMTP rate limits due to multiple health check executions.
  The logic checks for a temporary file (/tmp/email_sent) to determine
  if the email has already been sent. If the file exists, the email
  is skipped, but the health check continues by verifying the HTTP service.
  Refer to the conversation with ChatGPT (https://chatgpt.com/share/67898c3f-2c1c-800f-861c-47dcbe109135)
  on January 16, 2025, for the background behind this complexity.

  Additional it is also checked if the host is reachable
#}

    healthcheck:
      test:
        - CMD-SHELL
        - >
          if [ ! -f /tmp/email_sent ]; then
            echo 'Subject: testmessage from {{ domains | get_domain(application_id) }}\n\nSUCCESSFULL' | msmtp -t {{ users.blackhole.email }} && touch /tmp/email_sent;
          fi &&
          curl -f http://localhost:80/ || exit 1
      interval: 1m
      timeout: 20s
      retries: 3
{{ "\n" }}