You'll have to use your judgment but having employees send you more than what you'll classify as a "reportable complaint" isn't completely a bad thing. You can weed them out at the higher level and re-route them as necessary. This approach is provides you with an opportunity to ensure that you do not miss any reportable complaints or issues.
One thing you can do is use these as examples in your training to demonstrate what is reportable, and what will just be answered. You'll refine your processes as you gain experience, but I would train that "when in doubt, consider it reportable."