I have been unable to find any suggestions for what can be causing the following: the user is attempting to Flag a message for follow-up and receaives and error message the "The function cannot be performed because the messages has been changed." The user insists the message has not been changed; he just received it. I have no experience with using this feature; can anyone provide any ideas? Could this possibly happen if somehow the follow-up time has already passed? A clumsily edited JPG screen capture of the error is attached.

Thank you