We noticed a disabled System plug-in in our Confluence 5.1 (download) called Confluence Email Gateway. We enabled it, and now we have this new button in the Create dialog:

When you click on that, you get

I would love to use this feature, but maybe it is only in development? There is no help anywhere on the web for how to set it up - we tried setting up a POP email account in the back-end, setting up the scheduled task, etc, but couldn't get it to work.
Does anyone know how to work this?