Outlook Web Access allows you to set a message importance of high or low to any message you send or post, including new messages, replies, and forwards. Messages not designated as high or low have a normal importance.
To set the importance level, in the message or posting screen, on the toolbar, click Importance: High (the exclamation point) or Importance: Low (the down arrow).
To set message options
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To set Importance to HIGH, click the red exclamation mark 
- To set Importance to LOW, click the blue down arrow
