Users select authorized email subscription lists and assign a retention policy to them (quantity or age). Only messages that meet the requirements, for that email list identification (sender, directly addressed, subject, size, and combination thereof), are maintained in the mailbox and the rest are automatically deleted. This helps reduce clutter and consumption. ideally it is run on the server side on receipt but it could be a client side rule or even folders with rules or a combination of the client side rule and a folder retention policy..