Change the database size limit for Exchange 2003

Exchange 2003 ships with a limit of 16 GB (and for SP2 the default was increased to 18GB), but the maximum you can set is a whopping 75GB. So, here's how...

To configure the database size limit for a database:
1.   On the computer running Exchange Server, start Regedit.exe.
2.   Open one of the following registry keys:
�   To configure the database size limit on a mailbox store, use the following registry key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\Server name\Private-Mailbox Store GUID
�   To configure the database size limit on a public store, use the following registry key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\Server name\Public-Public Store GUID

In order to view this value you should use a tool like LDP.exe or ADSIEDIT.msc (both can be found in the Windows Server 2003 Reskit Tools - Download Windows 2003 Reskit Tools).

Navigate to the following DN: CN=Mailbox Store (servername),CN=First Storage Group,CN=InformationStore,CN=servername,CN=Servers,CN=First Administrative Group,CN=Administrative Groups,CN=Organization name,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=domain,DC=com

Note the objectGUID attribute of each store, then find the appropriate value in the registry path mentioned in step #2.

3.   Create a new DWORD entry called "Database Size Limit in Gb" and give it the appropriate value for maximum database size in GB.
For Exchange Server 2003 Standard Edition type a value between 1 and 75 (the default is 18 GB).
For Exchange Server 2003 Enterprise Edition type a value between 1 and 8000 (the default is 8000 GB). Click OK.
Note: Entries should be in decimal format.
Note: The setting in Exchange Server 2003 Enterprise Edition is useful when you want to limit the store size, mostly due to hardware restrictions.
4.   Create a new DWORD entry called "Database Size Buffer in Percentage" and give it the appropriate value between 1 and 100 to specify when you want events to be logged in the application log in Event Viewer to warn you that you are nearing the maximum size for a database.
The default value of 10 (i.e. 10%) will result in warning events to be logged when you have 10 percent capacity left before you reach the maximum size for that database.
5.   Create a new DWORD entry called "Database Size Check Start Time in Hours From Midnight" and give it the appropriate value between 0 and 23 to specify when you want Exchange to check the database size.
The default value of 5 results in Exchange Server checking the database size 5 hours after midnight (i.e. 5:00 AM).
6.   Close Registry Editor.

You should dismount and mount your stores, or restart the Information Store service for this mod to take affect.