Hi Niki,

I work at a manufacturing site where employees have a lot more contact with supervisors so my experience may not be relevant.  I have found that when we have used the suggestion box, most people who have used it do so to give anonymous messages.  Most are not very actionable - complaining about something that we are unable to act on or lacks the big picture perspective on the issue.  Unfortunately, we aren't able to follow up and often aren't able to do anything about it.  It creates a lose-lose scenario where the employee probably feels like we didn't do anything and we aren't able to discuss with the employee.

I would suggest requiring people to identify themselves.  That way, you can at least follow up on every submission. 

Another idea is to have supervisors hold one on one meetings with their employees at some interval where they ask a few questions that gauge the employee's work experience and even questions about the manager's own performance (Is there anything I can be doing better as your manager?).  Hold a training beforehand with supervisors to prep them for the meetings.  Hopefully that would be a good way to keep employees engaged and the communication flowing!