Well, I just figured that there is some delay. Say N900 checks email hourly alwasy at 12:00, 13:00 etc. For any given e-mail received during 13:01-13:55, if I read it before 13:55 (or so, I am not sure yet), I get a notification. If I do not read it or if the mail arrivers during 13:55-13:59, even if I read it before 14:00, I do get a notification.

WEll, I can live with that I guess.