How do I show if I am the BCC'ed recipient in Mail.app? I recently received an email from a collaborator in which I was the BCC (Blind Carbon Copy).  The original "To:" recipient was another collaborator who has a very similar email address to mine.  Because of the similarity in addresses, and because I didn't see anything indicating I was a BCC (even in the detailed header information), I responded back to the original sender and the "To:" recipient pointing out the "mistake."

Obviously this defeated the whole purpose of being BCC'ed by the original sender.

Is there a way in Mail.app to show if I am the BCC of an email?  I am not interested in seeing other BCC's on emails I receive.  This was on Lion, if that makes any difference.
(Sorry for the lack of screenshots; I'm writing from a Windows machine right now)

Go to Mail > Preferences > Rules

Click "Add Rule"

For Description, enter "BCC"
For the conditions, select "Any Recipient" "Does not contain" and enter your address in the third field
For action, select "Set Color" "of background" "Purple" (or whatever color you chose)
and click OK.

From then on, incoming messages not sent "To:" or "CC:" you will be marked in that color.