TLS is an Abbreviation of Transport Layer Security.

The term "Implicit TLS" refers to the automatic negotiation of TLS whenever a TCP connection is made on a particular TCP port that is used exclusively by that server for TLS connections.

The term "Implicit TLS" is intended to contrast with the use of StartTLS and similar commands in POP, IMAP, SMTP, LDAP Message Submission, and other protocols, that are used by the client and the server to explicitly negotiate Transport Layer Security on an established cleartext TCP connection.

Due to StartTLS Implementation Vulnerabilities lead Ldapwiki Preferring Implicit TLS on its own ports

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