HKLM\SYSTEM\CurrentControlSet\Services\MSExchangeIS\[ServerName]\Private-[ObjectGUID]

Create a REG_DWORD key called Database Size Limit in GB and set the value to 75. This will enable the database to go over the 16GB limit up to 75GB. You can select any value between 1 and 75 for a custom database limit if you only have 36GB of disk space, no use setting the limit to 75GB.