Do you want to be know when you are BCC'd on a message so you don't Reply to all?
For a gentle reminder, configure a Rule to set a flag on messages where you aren't in the To or Cc fields. You can even set the flag text to say "Do not reply to all" or other text of your choosing (choose the For action in a number of days option and type over 'For Follow up').
Published October 11, 2005. Last updated on June 17, 2011.