1. In the reporting console Right click at the Top of the Tree and select Custom Report.
2. Click Next on the Welcome screen
3. On the Data Source Tab select “Mailboxes - Mailbox Size Most Recent”
4. On the Fields screen select “Primary Mailboxes Size KB” and Server
5. Click next on the Filter screen and on the grouping Screen select Server
6. On the Format field select the “Advanced Summary Calculations” button
And check of Avg and Primary Mailboxes Size KB box and uncheck the Show details records and then finish out the wizard and save the report.
