What you are asking is why outlook connects to exchange20 13 with and without encryption.

Security policy and configuration, client settings.

1. security policy and configuration: organizations can enable or disable different levels of encryption on Exchange20 13, such as transport layer encryption (TLS) and encryption and signing of e-mail content. These security policies and configurations will vary according to the needs, compliance requirements or security considerations of the organization.

2. Client Settings: The Outlook client itself can also be configured to use specific encryption options. In the account settings of Outlook, you can specify options such as using encrypted connection or clear text connection.