Is there a script which will allow me to send an email to users when their mailbox is reaching 10% of their maximum limit. With the growth in the use of Iphones - alot of my clients are IMAPing in and leaving everything on the server.

Where as previously 250MB was perfectly fine, im now running 750MB+ per mailbox. To ensure my clients dont miss any mail, I would like an alert when they are reaching 10% of their total limit.