Reference Guide

Top 10 Microsoft Exchange Server 2003 registry hacks

Discover our top 10 Microsoft Exchange 2003 registry tweaks that will optimize Exchange Server performance while automating time-consuming administration tasks.

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Learn how to modify the registry to disable unauthorized use of .PST files; allow batch files and bulk mailings; enable drive mapping in Exchange Server 2003; troubleshoot Exchange ActiveSync errors; and download and install Exchange Intelligent Message Filter (IMF) updates automatically.

Important: Modifying the registry can be dangerous. An incorrect registry modification can destroy Windows and/or your applications. Perform a full system backup before continuing.

Please also note that Exchange Server 2003 registry strings referred to in this article are comprised of one line with no spaces.


 Lotus Notes URLs won't hyperlink in OWA and Exchange 2003
 Disable the use of Microsoft Outlook .PST files in Exchange 2003
 Optimize Exchange Server 2003 database maintenance
 Modify BADMAIL behavior and reporting in Exchange 2003
 Allow batch files and bulk mailings in Exchange 2003
 Enable drive mapping in Exchange 2003
 Configure Exchange 2003 to ignore zombie ACLs and ACEs
 Enable automatic Exchange IMF updates via Microsoft Update
 Troubleshoot ActiveSync error in Exchange 2003 SP1
 Override OWA attachment size limit in Exchange 2003

  Notes URLs won't hyperlink in OWA and Exchange 2003 Return to Top

Outlook Web Access will not recognize Lotus Notes URL links contained in Exchange 2003 email. To fix this Notes/Exchange compatibility issue:

Under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
, create a new Multi-String Value with the name AdditionalSafeURLScheme. Set the value to NOTES. You can add more protocols by comma-delineating them.

NOTE: If you have a front-end/back-end environment, you'll need to configure this change on both the front-end and back-end Exchange servers. Also, this only works on Exchange Server 2003 SP2 or higher.

  Disable the use of Outlook .PST files in Exchange 2003 Return to Top

To disable the use of Microsoft Outlook .PST files in Exchange Server 2003:

Create or modify the DWORD registry value: HKEY_LOCAL_MACHINE\Software\Microsoft\Office\11.0\Outlook\DisablePST. Set the value to 1 to disable .PST files, or 0 (default) to enable them.

Note that .PST files already located in a user's email profile will still be functional. Therefore, you should manually remove all .PST files from the profile prior to setting this value. This also includes disabling the auto-archiving feature, which takes advantage of .PST files.

  Optimize Exchange Server 2003 database maintenance Return to Top

The registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS
(or Public-GUID for public folder stores) can be used to control the amount of time that is used at the end of the maintenance cycle for online defragmentation.

Create a REG_DWORD key named OLD Minimum RunTime (this key is case sensitive), and assign it a value that reflects the number of minutes that you want online defragmentation to run as a part of the maintenance cycle.

You can also control the amount of time that the online defragmentation process runs after the maintenance cycle completes. To do so, go to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS
(or Public-GUID for public folder stores). Create a REG_DWORD key named OLD Completion Time (this is case sensitive).

Assign this key a value that reflects the number of seconds for which the online defragmentation process should run. For example, a value of 3600 would cause the process to run for 3,600 seconds (i.e., one hour).

In most cases, you probably won't have to adjust the registry keys, but you should make sure that you optimize the Exchange 2003 database maintenance interval settings for each store for your particular server.

  Modify BADMAIL behavior and reporting in Exchange 2003 Return to Top

Turning on BADMAIL reporting in Exchange 2003 SP1 requires a registry edit. This also allows you to set BADMAIL behavior. To modify BADMAIL behavior, edit a DWORD setting in HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SMTPSVC\Queuing.

The value to add or change, MaxBadMailFolderSize, is the maximum size in kilobytes allotted to each BADMAIL folder. Once this amount of space is exhausted in a BADMAIL folder, no more messages will be written to it.

Set this value to -1 (decimal) to allow for an unlimited folder size (i.e., the pre-SP1 behavior). Setting it to 0 (the default in SP1) will not write to the folder at all. Note that newer messages do not delete older ones; once the folder size has been reached, no new messages are written.

  Allow batch files and bulk mailings in Exchange 2003 Return to Top

To allow batch files and bulk mailings in Exchange 2003:

  1. Open the registry on the Exchange Server 2003 computer and navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchange
  2. Add a new key (not a value, but a whole subkey) named: MaxObjsPerMapiSession.
  3. Within this key, add two DWORD values: objtMessage and objAttachment.
  4. Set the value of objtMessage to the maximum number of message objects that can be automated at one time.
  5. Set the value of objAttachment to the maximum number of attachment objects that can be automated at one time. A good starting value for both of objects is 500.
  6. Close the registry. The changes will take effect immediately.

  Enable drive mapping in Exchange 2003 Return to Top

Exchange 2003 includes Installable File System (IFS) support for the Exchange store, but unlike Exchange 2000, it is not mapped by default to a drive letter (normally the M: drive) when Exchange is installed.

To manually re-enable the drive M mapping for Exchange 2003, edit the registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EXIFS\Parameters and add a new String value with the name DriveLetter and the value M. Choosing a different value will set the drive letter appropriately. If you remove or add the drive letter by changing or removing the DriveLetter value, the entire server must be rebooted to resynchronize.

  Configure Exchange 2003 to ignore zombie ACLs and ACEs Return to Top

Microsoft designed Exchange Server 2003 to co-exist with Exchange 5.5, if necessary. Unfortunately, the complexity of co-existence and the vast differences between the two versions of Exchange can create problems with access control entries (ACE) and access control lists (ACL).

One solution is to create a registry key on your Exchange servers to configure Exchange 2003 to ignore zombie ACLs and ACEs.

  1. Open the Registry Editor on the server and navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services \MSExchangeIS\ParametersSystem.
  2. Next, create a REG_DWORD value named Ignore zombie users.
  3. Finally, assign this registry key a value of 0x1. This will instruct the server to ignore zombie ACEs and ACLs.

If you want Exchange to recognize zombies for some reason, you can either set the registry key value to 0x0 or you can delete it completely.

  Enable automatic IMF updates via Microsoft Update Return to Top

Microsoft issues a new version of Exchange Server's Intelligent Message Filter (IMF) approximately twice a month (generally on the first and third Wednesday).

What many Exchange administrators don't realize is that Exchange 2003 SP2 and later versions can be set up to download and install new versions of IMF automatically through the Microsoft Update website.

To enable automatic IMF updates on Exchange 2003:

  1. Open the registry and edit the key HKEY_LOCAL_MACHINE\SOFTWARE
  2. Insert a new DWORD value named ContentFilterState and set it to 1.
  3. Navigate to the Microsoft Update website and click the "Custom" button to scan for optional updates. If a newer version of the Exchange Server IMF filter is available, it will be listed under available updates.

  Troubleshoot ActiveSync error in Exchange 2003 SP1 Return to Top

To troubleshoot Exchange ActiveSync error HTTP_500 in Exchange Server 2003 SP1:

  1. Open the Registry Editor and navigate through the console tree to: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MasSync
  2. The Parameters container should be empty by default, but you must add a value to this container. To do so, right click on the Parameters container and choose New -> String Value from the menu.
  3. Assign the name SMTPProxy to the new value. Keep in mind that the registry is case-sensitive.
  4. Right click on the value that you created and choose Modify from the menu.
  5. When prompted to enter string data, enter the problematic SMTP domain name in ActiveSync. For example, suppose that your organization's primary SMTP domain is, but ActiveSync is having problems with a secondary domain named In such a case, enter as the data for the new SMTPProxy value.
  6. Click OK, and navigate through the registry tree to: HKEY_LOCAL_MACHINE\CurrentControlSet\Services\MSExchangeWEB\OWA.
  7. With the OWA container selected, look for the value: DisableSMTPMailboxAddressing. If this value exists, you must disable it by right clicking on the value and choosing Modify from the menu. Then set the data value to 0.
  8. Close the Registry Editor and restart the IIS Admin Service by opening the Service Control Manager, and right clicking on the IIS Admin Service. Then select Restart.

  Override OWA attachment size limit in Exchange 2003 Return to Top

To override the attachment size limit for OWA public folder posts (default attachment size limit is 1 MB) in Exchange Server 2003:

  1. Open the registry on the computer running Microsoft Exchange and navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services \MSExchange
  2. Under OWA, create a new DWORD named Message Size Limit.
  3. Set Message Size Limit to the number of kilobytes you want the maximum attachment size to be. For instance, if you set this value to 2048 (decimal), a maximum message size of 2 MB will be enforced.
  4. Restart the Exchange Server information store.

This was first published in April 2008

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