So, you have deployed default retention tags to delete mail after a certain age. You have also given users access to a personal tag to let them keep some stuff longer. Now you want to audit to see if any of your users are abusing the personal tag.
This script allows you to specify a date and outputs a count of emails older than that date in each user mailbox.
This script borrows much from Glen's Exchange Dev Blog (http://gsexdev.blogspot.ca/2014/05/ediscovery-script-for-reporting-on.html).
This script utilizes the EWS Managed API, so you need to install that first: http://www.microsoft.com/en-us/download/details.aspx?id=35371
See here: http://gallery.technet.microsoft.com/office/Search-for-count-of-items-d2ec2bfa