Hello, @vibhi
The TLS setup is to be configured based on your preference. If you refer to the Configuring TLS on Mattermost Server. In case of setting up SSL on your server, you will need to make configuration changes on System Console > General > Configuration . I came across users utilizing Cloudfare for encryption, so it is another option that you can consider :
A simple encryption is to use a official signed SSL certificate issued by a certificate authority (for example, Let’s Encrypt) to secure communication. You can also consider setting up a proxy with TLS if you prefer a better security setup as well as performance.