If you list some okaddrs, iftocc will use them in place of $RECIPIENT. It exits 100 if none of them are listed in To or Cc.
For example, with qmail 1.03 and above, you can put
|bouncesaying 'I do not accept Bcc.' except iftocc
into your .qmail file to reject blind carbon copies (including messages from mailing lists), or
|condredirect me-blind except iftocc
to forward all blind carbon copies to me-blind.
WARNING: If you create a .qmail file to invoke iftocc, make sure to add a line specifying delivery to your normal mailbox.