To be able to send a Vereigned email, it must be signed through the Vereign system. This is exactly what Chrome plugin or Roundcube seamlessly do for you.
After you install the Vereign plugins and send emails with either of the plugins enabled, you get the following main benefits:
You have your emails pass through the Vereign system.
You have an inbox in the Vereign dashboard where you can monitor and keep a history of all your securely stored emails.