I have made a minor change to the default preferences for Webmail. Now the first time you log into webmail on or after the 1st of a month, you will get a screen that asks you if you want to perform maintenance on your account and then there are check boxes for a few things. Such as moving your Sent folder to Sent-oct-2004, removing Sent mail that is more than 6 months old, and removing any email in your Trash that is more than 30 days old. Each user that gets this screen can choose if they want to perform these operations, skip them, change the settings on them, etc.
If anyone thinks this is a bad idea, please let me know. I am hoping that this will help people from going over their quotas with large Trash and Sent mail folders.