The way I mark all read messages in a folder as read is I select all, hit command-alt-m, which makes them all unread, and then hit it again to mark them all as read. Not the most elegant thing, but it works.

Whoa - that seems like a lot for such a simple task.

Command-A, Command-Shift-U works for me (mark all as read).

What do you mean by filtering outgoing messages?

Right-click (or ctrl-click) on a mailbox in the mailboxes drawer. Choose "Mark All Messages as Read" from the pop-up menu.

Filtering outgoing messages: If I send an email to address A I want to be able to apply a rule to that email that says "Move all emails addressed to address A into folder B" instead of having them accumulate in the Sent mail folder.

Russ: I must be really missing something because that menu item doesn't appear in my contextual menu.

Aaron: in my vers of Mail.app it's Cmd-Opt-M, what vers are you using?