You know the problem..
A user asks you "Why does my mailbox icon display that I have 4 unread emails, but there are no unread emails in my inbox or folders?"
The answer is often because:
Currently marking mails read/unread is rather slow in iNotes. It is fast in Notes via the INSERT button.
Maybe in iNotes you could have a behaviour similar to other web mail client (outlook.com e.g. if I may name it...) where you click an icon on the mail itself. It could ...