Glen's Exchange and Office 365 Dev Blog

Messages that are stored in Exchange can be flagged in a number of ways to indicate different states to the user or as an effective method to prompt the user to action (or make them remember to do something). Unread/Read Flags  The most commonly used Flag in Exchange is the Unread/Read Message flag which is used so when a message arrives in Mailbox a user can track which messages they have read. In EWS this flag is surfaced in the API in the form of a Strongly type property isRead   https://msdn.microsoft.com/en-us/library/office/bb408987(v=exchg.150).aspx  . (The underlying Store property that back this is PidTagMessageFlags property https://msdn.microsoft.com/en-us/library/ee160304(v=exchg.80).aspx   which is a bitwise flag representing many states of a message). The other place the Unread Message flag is surfaced is on the Folder object in the guise of the Unread Item count. So in the below example we Bind to Inbox folder and we can look at the Total Number of Items in a Folde