Viewing unread emails

This is a question I am getting from users

We are still having problems with viewing unread emails. Also, some email that have not been read are coming up as read. What’s going on?

The server can client are 6.0.4 redhat is the server adn win xp is the workstations.

Subject: Viewing unread emails

“We are still having problems with viewing unread emails.”

Such as?