What is TLS?

TLS stands for “Transport Layer Security”. It is a protocol that is responsible for encrypted communication between a client and a server. TLS is actually the further development of SSL, but since the term SSL is better known, it is still used as a name for both protocols.

When transporting e-mails, it is important that the e-mails are available in unencrypted form on every mail server they pass. Therefore, only the transport route, i.e. only the route between the mail servers, is secured.