In prior versions of Notes, there was an option for the user to choose whether or not to mark emails as read when viewing in the Preview pane. This preference setting seems to have been removed in the latest versions. Now, emails are not marked as read in this mode, unless the user manually marks each item as read. There should be an option to do this automatically without an additional step by the user, as in prior versions. Current version is 10.0.1 FP5 on Mac OS.