Mail Satellite, which I'm running at the moment is altogether curious...
It's listed as $15 shareware on
MacUpdate (for an earlier version than clicking on "Download" delivers), but it's NOT listed on
its dev's website, nor do I see any way to pay for it. (I see ~/.../Mail Satellite.app/Contents/Resources/
THPurchasedInfoWindowController.nib, but if it's what it sounds like, its purpose has yet to be revealed. I wonder if there's an undisclosed trial period after which it will jump out of the woodwork and say "Boo!" just when I've decided that it's purposeless?)