Using Mail with the latest OS X, I have one email (an EIC notification, no less) that will not delete. When I try to delete it, it turns gray, and I have the option to undelete it, but it always remains in the Inbox. I have completely closed and restarted Mail, as well as restarted the iMac, to no avail. I've never seen this before, even on a Windows PC. What the bunk?