Opportunistic TLS
We had to upgrade our mail gateway/anti-spam software on Sunday because one of our vendors requires us to use encryption when exchanging emails with them. The easiest solution is to use opportunistic TLS, where the server will always try to connect to the other server using the TLS protocol. If the other server supports TLS, then traffic is encrypted. If not, then the email is sent using just regular SMTP without encryption.
This is actually …