If you use your email to send both secure and un-encrypted messages, you will use the #secure method so the service can determine which messages should be encrypted. Simply add #secure to your message’s subject line. It is not case sensitive, meaning you can use #SECURE, #Secure, #secure, and so on.
If you want all of your outbound mail to be encrypted, please let us know. We can configure your account so it will work that way. This would be especially useful for customers who have registered a domain exclusively for sending encrypted messages, or are required to encrypt all outbound email.