It is possible for an account administrator to see how many messages their users are sending, receiving, and the volume of units charged.
Parent account administrators can view individual accounts or sub-accounts, and it is also possible to filter by email address or username and specify a date-range. The report can also be downloaded from an emailed CSV.
Simply select the date range and the Account from the fields at the top of the screen, as well as the email address by which you would like to filter if you are only looking for stats on a specific user, and then click Run Report:
The User Usage Report link will appear in the Reports menu.