Mark Follow Ups as Completed

Once you have completed a follow up, you can mark the message as completed.  

To mark a message for follow up, select the message and then click the Mark for Follow Up button on the Follow Up tab on the toolbar, or select Follow Up/Mark for Follow Up from the File menu.

An icon will be displayed next to the message indicating that follow up has been completed.

All other users who received the same message will also have theirs marked as completed.  This lets other users know that no further follow up action is required.