Increasing the Exchange 2003 Mailbox Database Size limit

"rIs your Exchange 2003 Server at its limit for Mailbox space?

The standard database size limit for Microsoft Exchange 2003 is 18 gigabytes (this went up from 16 gigabytes). However, most companies running Exchange 2003 are encountering their 18 gigabyte limit. At that point, most companies will upgrade their Exchange Server to Exchange 2007 or 2010. But if you either don't want to do that, or cannot afford it, there is a way to increase your limit up to 75 Gigabytes!


Service Pack 2 for Exchange 2003 has a nice new feature that allows you to increase your database limit to 75 Gigabytes with a small registry key change  (or creation).

To do this, follow these steps:

1. Open Registry Editor by clicking Start, click Run, type in "regedit" and click OK

2. Modify one of the following registry subkeys;

  • For the mailbox store, click the following registry subkey: HKEY_LOCAL_MACHINESystemCurrentControlSetServicesMSExchangeISServer namePrivate-Mailbox Store GUID
  • For the public folder store, click the following registry subkey: HKEY_LOCAL_MACHINESystemCurrentControlSetServicesMSExchangeISServer namePublic-Public Store GUID
3. After navigating to one of these, click edit, mouse over new, then choose DWORD Value
4. In the New Value #1 box, name the registry entry Database Limit Size in Gb and press Enter

5. Right click your new entry you created above and choose Modify

6. Click Decimal and then type a number between 1 and 75 in the Value Entry box (the number represents the GB limit you want to set for your store)

7. Click OK and close the Registry Editor.

Now that the registry entry has been created, we need the restart the Microsoft Information Store


1. Click Start, click Run, type "services.msc" in the box, and press OK

2. Under the Services list, right click Microsoft Information Store  and select Restart.

3. Once it has been restarted, close Services and open Event Viewer

  1. Click Start, click Run, type eventvwr, and then click OK.
  2. In the Event Viewer tool, click Application.
  3. Double-click event ID 1216 to verify that the database size has been set successfully.
If it has been set successfully, then congratulations! Your Database size has been increased!
Rutledge Daugette
CEO and Founder

Founder of TechRaptor with a love of video games (B.S. in Game Programming) and technology. Started TechRaptor to create a place where people could come for quality content.