I'm sure I have read all my new mail messages, yet that envelope won't stop flashing! Any suggestions?

Not off the top of my head... have you tried clearing your browser cache?

I decided to empty my messages and the flashing stopped. Don't know why I had kept all the old ones anyway.
Unfortunately, I suspect one of them was never read, and that's why the envelope was flashing.
Oh, well.... somebody probably thinks I avoided them.

Yes, if a massage wasn't read, the envelope will keep flashing.

Hopefully the person will contact you again!