If you are running a business and have customers having emails that are silently being dropped, adding a "verify your email address" page in your process is probably a good step to have anyway.
Google's Postmaster tools all show "No data to display at this time. Please come back later. Postmaster Tools requires that your domain satisfies certain conditions before data is visible for this chart."
Microsoft's Safe Network Data Service shows *"No data for specified IPs on this date" for every day.