Thanks everyone for the great suggestions.
After changing my password I have not identified any new unusual activity on my email account.

Neptune0z:
I am interested in your idea about spreading some "honey".

If I cease using my regular account and then set it up with the old password reset and send some emails to the old address with some interesting "misinformation" of potential interest to a hacker, how do I set up the sniffer and links you mentioned?

nihil:
My guess is whoever is peeking at my email was maybe in a rush on occasion and forgot to mark "unread" on some of the messages looked at that I had not previously opened. As to why a message would show "unread" after I had opened it , I can only assume I am dealing with a sloppy hacker that might be lured into a "honey patch" if I can set one up.
David