I receive a ton of email from advertisers and some advertisers send me multiple emails per month/week. I would like to keep my inbox clean by using a new type of rule that triggers Yahoo to automatically delete all old emails from a specified email address, except the most recent one. That way I can stay aware of new offers, but not have to manually clean out my inbox. This is better than the existing "find all" spyglass search, because it requires only initial setup one time.