How to flag an email and send to other recipients in Outlook 2013?

If you want to encourage people to reply a message or you want to request other actions from them, you may send a flagged message to them.  An item will be added to recipients’ to-do list.

1. In the new message, on the “Message” tab, click “Follow Up”.
   
2. Click “Custom”.
3. Check the “Flag for Recipients” box, select the time to send the reminder.