The default privacy setting for Loop Messaging is: "Only researchers whose message invitations I have approved." You can change this setting at any time on your profile settings page.
You are required to enter an invitation message which properly introduces yourself to the other user, which they need to approve. Once approved, private messages can be exchanged freely.
If the message has been sent correctly, the status of the conversation will appear as "Invitation Pending", as displayed below:
Messaging invitations can be approved in the conversation panel. It is only possible to exchange messages after acceptance:
Please note, there is no notification to the sender if you decline an invitation. The status of the conversation will stay "Pending".
In the event that you accidentally decline an invitation, it is possible to undo this operation to allow the other user to contact you: