Google Workspace supports TLS; however, for a secure TLS connection, TLS compliance must be set up by both the sender and the recipient. If the receiving server doesn't use TLS, Gmail still delivers messages - but the connection is not secure. By adding the Secure transport (TLS) compliance setting, Gmail always uses a secure connection for email sent to and from specified domains and email addresses.
Learn how to set up TLS compliance in Google Workspace here.