Answer
Below is a great way to find out if your Superstream message was successfully sent:
After you have sent your Superstream message/s, go into the Superstream Mailbox. Click Check Responses to refresh the mailbox with the latest message info from the Superstream network. You might not have any responses yet, but don't worry. This is common.
Using the date and message status filter boxes at the top of the mailbox, search for the messages you've just sent.
Click View beside the message you'd like to check.
If your Superstream message was successfully processed by the network, and forwarded to the super fund there will be a value beside Conversation ID. This acts similarly to a tracking number on a parcel and is the unique identifier for that particular message. It can be provided to a super fund if needed.