I recently received this question:
" I'd like all items that have been received more than an hour ago (or another period of time) to be marked. Is this possible to do with Automatic formatting? "
To the best of my knowledge, you can't apply automatic formatting to items "by the hour". At least I haven't figured out a way to do this and I've tried many variations of '1 hour ago' in the rules.
You can use a specific hour, such as 12 PM in a "between" rule and a date in the past. Create the automatic formatting rule to read
Received between 12 PM and 6 months ago
Or
Received between 12 PM and 1/1/2009
It would also be possible to use VBA to mark messages read, flag them or move them as they age.
There are Outlook add-ins that can act on old mail after a period of time. (I use Auto-Mate.) These add-ins are client side so the mailbox needs to be open in a profile.