Twilio SendGrid Enforced TLS API

The Twilio SendGrid Enforced TLS API allows you to specify whether or not the recipient of your mail send is required to support TLS or have a valid certificate. Twilio SendGrid sends all emails with [Opportunistic TLS](https://sendgrid.com/blog/myth-opportunistic-tls-email-privacy/) by default, meaning email is sent with TLS, and if the recipient's inbox provider does not accept the TLS encryption, we then send the message unencrypted.