You can request a Notification when your message is delivered to the recipients.
Select the Delivery Notification (Notify when Delivered) option to request a DSN. DSN messages sent back to your INBOX tell you that your messages have been successfully delivered to the recipient Mailboxes. They do not tell you if the recipient has actually seen/read your message.
Note: The DSN is guaranteed to work only when you send a message to other users on the same CommuniGate Pro Server. If a message is sent to a remote recipient, the remote server that serves that recipient account may or may not support the DSN feature. In many cases your CommuniGate Pro server can detect that a remote server does not support DSN. In this case your server will send you a DSN message itself, telling you that your message has been relayed to a remote host.