We can disable the use of opportunistic SSL/TLS encryption in the delivery of your email messages.
This will require that all messages are delivered over an encrypted connection. If a message is injected for delivery and the recipients' mail server does not support encryption, then we will not revert to an unsecured delivery mechanism and we will consider the message to have failed delivery. This is for specific-use cases with our service and for security-concerned organizations, but not recommend for most senders. Many receiving mail servers still do not support encryption and this could cause a large number of messages to fail.
By default, our platform will ignore any certificate errors or warnings that may occur. This does reduce the security of resulting encrypted the connection. We can upon your request only deliver messages securely to domains with properly verifying certificates. This is commonly used in conjunction with Force SSL/TLS options. Requiring certificate validation without forcing the use of SSL/TLS is pointless as by default we would revert back to a totally unsecured delivery mechanism.