Store.IsOpen Property (Outlook)
Returns a Boolean that indicates if the Store is open. Read-only.
This property supports both Exchange and non-Exchange stores.
IsOpen only indicates if the store is open. It does not indicate if the store is offline, or if it is an Exchange mailbox or an Exchange Public Folder and the store server is down.
Because opening a store can impose a performance overhead, and Store.GetRootFolder and Store.GetSearchFolders will open a store if it is not already open, you can use IsOpen before deciding to call GetRootFolder or GetSearchFolders to minimize performance overhead.