When Microsoft Office Outlook clients are in an Exchange Server environment, users can share or delegate access to folders in their mailboxes. With appropriate permissions, a user can go to File, Open, Other User’s Folder as shown in Figure 1. Outlook maintains a list of most recently used (MRU) folders in this menu, as circled in Figure 1. The MRU list makes it easy to access resources users need on a regular basis. Recently, I was asked how to clear this list.

This seemingly simple task proved a little challenging. MRU lists are common throughout Windows and various applications, including Outlook. On the Windows Start menu in both Windows XP and Windows Vista, you can control whether or not recently opened documents or applications are stored and displayed. These Start menu MRU lists are configurable using the Windows GUI. For more information, see Microsoft Knowledge Base article 307875 “How To Display, Use, and Clear ‘My Recent Documents’ on the Start Menu in Windows XP.” In Outlook, we have to look into the registry to control similar lists.

There are several registry keys that store the MRU information for Outlook. The content is stored in binary format, and therefore specific entries can’t be edited. Deleting the key specific to the MRU will clear the values. If the DWORD values for the registry key do not yet exist in the registry, then there are no entries created for it yet in Outlook - for example, if the user has not opened another user’s folder, then the registry value for that MRU will not be present in the registry. Outlook will query the key at startup and recreate it if it’s missing. So, what registry key are we talking about?

The common MRU lists are stored in the following specific registry key:

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\\0a0d020000000000c000000000000046\

There are several DWORD values here that apply to specific MRU lists in Microsoft Office Outlook 2007 and Outlook 2003.

  • 101f0390 File|Open|Other User’s Folders
  • 101f035e Actions|New Mail Using (Stationery list)
  • 101f035c Insert|Signature (New Message)
  • 101f031e Move to Folder
  • 101f0449 Save Sent Items Folder

There are a few values specific to Outlook 2007 as well:

  • 101f042b Insert|Include|Business Card (New Message)
  • 101f0445 Recent Searches (Instant Search)
  • 101f0446 Search Address Books (Toolbar)

Figure 2 demonstrates the deletion of the key 101f0390 to remove the Open, Other User’s Folder MRU list in an Outlook 2007 profile named MM-William running on Windows XP. Outlook only reads these registry values at startup, so changes require a restart of Outlook to take effect if Outlook is open when the changes are applied.

When Outlook starts, it makes many queries of the local registry. To see this in action you can use utilities from Microsoft Windows Sysinternals Troubleshooting Utilities. For Windows XP, the Registry Monitor tool RegMon works well. On Windows XP SP2 and Windows Vista RegMon has been integrated into a more multipurpose tool called Process Monitor. Like a packet capture tool, these monitoring tools capture specific types of activity and present the data in log-style format. The resulting capture file can be quite large, but filters can be easily applied. Figure 3 shows a ProcMon capture while Outlook 2007 is being opened in cached mode on a Windows XP SP3 workstation. A filter showing only Outlook.exe entries has been applied. We can see Outlook querying the registry for the MRU entries we just mentioned. (For more information on Sysinternals, see the Learning Path accompanying this article.)

You can find another MRU that’s easy to control in the Locations field whenever you create a new appointment or meeting. This MRU has a slightly more user-friendly registry key to work with. To clear the meetings location MRU list delete the LocationMRU key from the following registry path: HKEY_CURRENT_USER\Software\Microsoft\Office\\Outlook\Preferences Like the Start Menu MRU keys, the LocationMRU key is also in binary and will be recreated with no entries when Outlook is started again. (See Microsoft knowledge base article 300579, “How to reset location list for appointments and meetings.”)

Some companies have a policy of keeping MRU lists cleared for security reasons. Most of the time, this applies to Windows in general and not to Outlook. However, if necessary, these registry entries can be pushed out through common centrally administered methods, including logon scripts or Group Policy. Other companies see value in the MRU lists. When migrating Outlook to a new computer, the DWORD values listed above can be exported and then imported into the registry of the destination computer. This will populate the MRU lists in the new Outlook installation.

Finally, you can also remove all the MRU lists for a specific profile by deleting the profile and recreating it. The MRU lists will not be recreated with the new profile. This may be a little drastic, especially if the profile is using Cached Exchange Mode and would have to recreate a new local copy of their Exchange mailbox.