Hate to get off topic here but, I have to disagree with you on quotas. Quotas are a good thing(tm). "Time Burden" being key here; anything the user can do, should be done by the user. Unless you have a bazillion admins (never seen that before) then the user needs to accept some responsibility for what I consider to be trivially easy.
I really don't care who you are, from peon to CEO, part of your job is proper e-mail archival. Keep things nice and tidy with filters. Set automated pruning according to your requirements. Every so often, delete some stuff by hand, or burn it to a CD.
It's just like any other type of filing. If you were an accountant would you leave a huge pile of bills and invoices on your desk until it was so big you couldn't get to your desk?
You knew the job was dangerous when you took it, Fred. -- Superchicken