title: TLS certificate installation in ejabberd for STARTTLS negotiation
body: <p>I read that ejabberd recommends to use STARTTLS negotiation for secure connection between communicating entities. When I install ejabberd, by default it comes with a TLS certificate. </p>
  
  <p>Then, why do I need to buy a certificate to install? what is the purpose of buying a new certificate from Certificate Authoririty since we have a default certificate?</p>
  
  <p>When I deploy ejabberd on the machine, how the default certificate will be used for my domain? How the default certificate will be verified by client?</p>