This test requires administrator access and access to an SMTP server supporting TLS, even if TLS is mis-configured i.e. not ready for production.
- Log in as an administrator
- Enable SMTP debugging
- Install https://moodle.org/plugins/local_mailtest
- Configure SMTP settings to use the SMTP server above w/o requiring TLS i.e. do not leave smtphosts empty and set smtpsecure to None
- Send a test email and look at the debug output. It should tell you about the TLS being available e.g.:
but you should not read about the client asking for TLS i.e. the debug output is missing: