In Email Security > Sender Notifications, you can enable the following notifications:
Enable sender notification for messages encrypted via TLS-Verify: Turn on the Enable toggle to send notifications to the sender each time the email is encrypted and sent via TLS-Verify.
Enable read receipts for messages encrypted via Registration Required and No Registration Required: Turn on the Enable toggle to send read receipts of recipients to the sender.
Enable sender notification for messages encrypted via Registration Required and No Registration Required: Turn on the Enable toggle to send a notification to the sender each time the email is encrypted and sent to the secure message portal.