Having IMAP client mark old moved messages as Read

Boy, I hope someone can answer this.

For the most part I use Apple’s OS X Mail.app client to handle my IMAP email on my DreamHost account, OS 10.4.8 if it matters.

Anyway, what’s weird is that for some reason that particular client marks as Unread any messages that get automatically moved to the old-messages folder, and if I click on that folder, all those messages suddenly get marked as Read as they should be.

I don’t think other clients do that, like Thunderbird, which I use on the PCs that I sometimes sit at.

Is there a way to structure a rule in Mail.app that will help to keep moved messages from appearing as Unread?

I hope my question is clear, it’s a strange problem and thankfully not that urgent, just more of a nuisance.

There is a Mark as Read rule. Can’t you add that to your auto-move rule?