How to Set a Reminder to reply to any message that you get in Outlook

• [Outlook 2003 users]
  Right-click the message you want to set the reminder for, point to Follow Up, and then click Add Reminder. In the Due By list, click the date when you have to complete the reply. In the second list, click a time. In the Flag color list, click the flag color you want, and then click OK.

• [Outlook 2007 users]

Drag the message directly to the To-Do bar. Right-click on the flag for email, and select Add Reminder. In the Reminder section, select the date and time you want the reminder to appear and click OK.
(In Outlook 2007, messages that you flag for follow-up not only show-up not only show up in the To-Do bar, but also in your task list and your calendar.)