How to enable TLS Encryption

There are two parts of enabling the TLS encryption.

To create and manage key certificates

1.                   Open IIS management console, Locate SMTP Virtual server, and then click properties.

2.                   Click Access tab, under secure communication, click certificate (it’ll setup new key cert) and Manage installed key certificate for the SMTP virtual server.

Key pair’s number of bits or size measures the security level. You can increase the security by increasing the encryption level from 40 bits to 128 bits. Make sure user is also using the same encryption level that you set or message will returned with non-delivery report.

To set TLS encryption levels for the server

1.                   Open IIS management console, Locate SMTP Virtual server, and then click properties.

2.                   Click the Access tab, and under Access control, click Authentication.

3.                   Click Basic authentication.

4.                   Select the Require TLS encryption check box.

The configuration gets complete here, but incase you like enable it for particularly Outbound or Inbound then follow these steps.

For Outgoing connections, click Outbound Security on the Delivery tab, and then click TLS encryption. Also, if a server you commonly connect to requires the use of TLS for all incoming connections, you can create a remote domain and click TLS encryption when creating the domain.