If you are a Highrise user, this new setting may be important for you. It allows you to send all outgoing email to the Highrise dropbox email address. Inside Highrise, the email gets automatically attached to the right person or Highrise creates a new person on the fly. See the Highrise email page for more information.
Every Gmail account has its own Auto-BCC setting.
Important: This feature works in Gmail 2 only!