Explanation/Reference:
Explanation:
Create a Send connector to send email to a partner, with Transport Layer Security (TLS) applied If you want to ensure secure, encrypted communication with a partner, you can create a Send connector that is configured to enforce Transport Layer Security (TLS) for messages sent to a partner domain. TLS provides secure communication over the Internet.
See step 2 below.
In the EAC, navigate to Mail flow > Send connectors, and then click Add-Add Icon.

In the New send connector wizard, specify a name for the send connector and then select Partner for

the Type. When you select Partner, the connector is configured to allow connections only to servers that authenticate with TLS certificates. Click Next.
Verify that MX record associated with recipient domain is selected, which specifies that the connector

uses the domain name system (DNS) to route mail. Click Next.
Under Address space, click Add-Add Icon. In the Add domain window, make sure SMTP is listed as the

Type. For Fully Qualified Domain Name (FQDN), enter the name of your partner domain. Click Save.
For Source server, click Add-Add Icon. In the Select a server window, select a Mailbox server that will

be used to send mail to the Internet via the Client Access server and click Add-Add Icon. After you've selected the server, click Add-Add Icon. Click OK.
Click Finish.

References: