Today when I logged on at work I suddenly had 46 unread emails/notes-messages. Well actually I hadn't.
It just happened that a person whom I had sent to and received from 46 mails had left the company and that her account had been deleted the night before. And Notes' account deletion seems to be quite thorough, this person's address was deleted from the Sender/Recipient fields of the messages I had received/sent. (Yes, I've now got lots of messages without any reference to a either Sender or recipient.) Notes now happily chose to flag the messages as unread because they were changed.
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