Add a flag to a message
Flags create a visible reminder that an action is due. When a message is flagged, a flag appears for that message in the message list. Flagged items also appear in the To-Do Bar, in the Daily Task List in Calendar, and in the To-Do List in the Tasks view.
In addition to flags, you can include a reminder that alerts you at a pre-determined time.
As you hover over flagged messages in the Task List, the details that are associated with the flag appear, such as the due date, the type of follow up that is needed, or a when a reminder will appear.
Do one of the following:
In an open message, on the Home tab, in the Tags group, click Follow Up, and then click a flag.
In a message list, such as your Inbox, click to the right of the item to set your default flag. For more default date options, right-click on the flag and select from the drop down list.