TLS encryption does not work
When trying to send a test message/newsletter using a custom SMTP method configured to use TLS encryption, you see the following error message: "unable to connect with TLS encryption".
PHP 5.6 or newer forces verification of the destination server's authenticity. If, for some reason, the server uses an invalid (or self-signed) certificate or your PHP has an invalid/missing certificate authority bundle, the secure connection will fail.
In the case of the invalid/missing certificate authority, please ensure that you host has a properly configured PHP installation that uses a valid certificate authority bundle.
If you are still unable to connect, it is possible that the destination server is using a self-signed certificate, which is disallowed by default. In this case you can use a custom hook to configure the secure connection (i.e., set SSL context options) and disable self-signed certificates and/or authenticity verification.
Please note that this opens you to negative security implications such as the man-in-the-middle attack.