Do you have TLS hosts I can test (Normal, Deprecated Version, Mandatory, None)?
test@CheckTLS.com is a normal TLS host. Per the RFCs, it will offer and optionally do TLS with any email sent to it. If the sender accepts the TLS offer and negotiates a TLS connection, the email will be sent encrypted, otherwise it will be sent in plain text. All emails are discarded.
test@RefuseTLS.CheckTLS.com does not offer and will not do TLS, so any emails sent to it will be in plain text. All emails are discarded.
test@TLSv1.CheckTLS.com only offers TLSv1. Use it to test an email system configured to not allow such an old and less secure version.
test@Invalid.CheckTLS.com does not exist in DNS. Use it to test what an email system does with an invalid domain name.
Mandatory TLS offers and forces TLS. It requires either a subscription or a single-use token (available on the test page).