Flag for recipient

This icon indicates that the received message has been flagged by the sender of the message and not by you.

If you want to do this yourself, create a new message and choose;

• Outlook 2003 and previous
  Press the flag icon; all flags during composing will be for the recipient
• Outlook 2007
  Click the Follow Up flag on the Message tab and click; Flag for Recipients…
• Outlook 2010
  Click the Follow Up on the Message tab and click; Custom…-> enable: Flag for Recipients

In Outlook 2003 the icon is a lighter red than the normal red flag icon and does not hold a colored background like colored flags do which you can assign yourself;

In Outlook 2010 the Sent Item of that message will hold a special icon to indicate it has been sent with a flag for the recipient;

Note 1: For an overview of icons used in Outlook and their meaning see this guide.

Note 2: If you set a custom text for the follow up text, this text may be blocked for the recipient.