I have found the mail app changes (in iPhone) so frustrating. First, hitting the right arrow to see the newer unread messages seems odd to me. Second, when i click it, and it opens the next newest message.... it does not automatically lower the unread message count right away. There is a long delay. And lastly, if you open an email that is a reply to a long string of an email (a lot of back and forth)... i cannot figure out the logical order of the message. The current message you are viewing is somewhere in the middle of the messages.. and if you are trying to scroll up or down to see what someone else had said before.... hard to find your way back to the current message.
Need to find a different mail app.