STARTTLS is a way to take an existing insecure connection and upgrade it to a secure connection using SSL/TLS. Note that despite having TLS in the name, STARTTLS doesn't mean you have to use TLS, you can use SSL.
The SBC notification system is base on email sending. With the STARTTLS support the communication will be encrypted between the SBC and the SMTP server.
To active the STARTTLS support just: