I use the “preview pane” feature in conjunction with the “Unread Mail” folder. I preview most e-mails in that pane.

Occasionally, after the 10-second delay or whatever I’ve set, as the item becomes “read” rather than “unread”, it moves the item from the “Unread Mail” folder. This happens relatively infrequently, perhaps one day per week, I have no idea why, but it’s an ongoing annoyance, since, upon reading e-mails I like to organize them or cache them in a project-specific folder (wherein they will never, ever be re-read).

Any thoughts?