We have taken the first steps towards an overall health check of your user panel. Currently, we have the following health pointers:

Bounce rate: Number of mails that have been rejected by the mail server in the organization
Spam report: Number of panelists where the message has been categorized as spam by the mail client
Block rate: Number of panelists that have blocked messages from the panel
No responses: Number of panelists, which have not opened the messages