I'm seeing more and more blank or meaningless SPAM emails (No attachment, link, Advertisement, or Phish attempt) sent to my employees. I assume they are sent with tracking software just to see if their address is in use or not. Is there anyway to check or verify this?
If you don't open the emails or have an email client that automatically loads images, you can't be tracked (except for exploits of course). The software won't install automatically. If your users don't click anything, they'll generally be safe. (of course, all the normal security precautions like anti-virus still apply)
You can check if there are any references to external sites in the emails. Check the source code of the emails, for example in Thunderbird using ctrl+U. Look for any links that might uniquely identify your users, such as:
Yes, KLM (Royal Dutch Airlines) likes to track stuff