The Mail icon in the Dock shows how many unread messages are in your Inboxes. Is there a way for it to count all unread messages, even the ones that automatically get routed to other mailboxes via rules?

For example, I have a mailbox set up for emails from my wife's accounts. Anything from her automatically shows up there. But if I get three messages from her, the Mail icon doesn't show it because those messages aren't under the Inbox.