问题 After quite a lot of debugging, I've refined a complicated Managed EWS problem down to the following two simple-ish test cases. The first one works, the second one fails: var view = new ItemView(100) { PropertySet = new PropertySet { EmailMessageSchema.Id } }; var findResults = ews.FindItems(WellKnownFolderName.Inbox, view) var bindResults = ews.BindToItems(findResults.Select(r => r.Id), new PropertySet { EmailMessageSchema.Sender }); // Sanity check Assert.AreEqual(1, bindResults.Count()); /