title: Send Confidential email through gmail api
body: <p>I am trying to send Confidential emails via gmail, although I am not sure it is supported. Via the gmail API, the User.messages fields do not seem to indicate whether an email is confidential or not. I retrieved a confidential and regular email via the v1 gmail api get method and the messages are identical. Is there a way send a confidential gmail email, either with the official api or other service?</p>