Deleted Items and Exchange 2016 Upgrade
The current email quota of 15 GB will remain in Exchange 2016 with one exception – the Deleted Items folder will now count toward your quota. If you use Deleted Items as extended storage, you need to clean out unneeded, unwanted, or even old email. You may create a .PST file to store on your computer where you can access any email that you wish to keep. Remember, if your Deleted Items folder is too large, you may not be able to send or receive email. For help contact your IT Pro or Tech Support at 573.882.5000.
— Oct. 19, 2016