ARCHIVED: At IU, using Outlook 2003, when I try to search the Global Address List using my IMAP account, what does the error message "unavailable critical extension" mean?

Note: At Indiana University, this document does not apply if Outlook is configured for an Exchange account. For more information about configuring your Outlook 2003 account to search IU's Global Address Book (GAL), see ARCHIVED: Search the Global Address List in Outlook using IMAP

You may experience problems using Microsoft Outlook 2003 when browsing an LDAP server's address book with more than 5,000 entries. Due to the large size of IU's GAL, if you are using Outlook 2003 with an IMAP account (for example, a Cyrus mail account), you may see the following error messages when you try to open the Address Book:

"Unavailable critical extension."

After you click OK, you'll see this error message:

"The action could not be completed."

The error messages implies that you cannot make an LDAP query. This is not so. The reality is that Outlook's Address Book simply cannot build a list for you to scroll through; that is actually the action that cannot be completed. You can still make the query; you'll just have to bypass the list that the Outlook Address Book builds. To do so, try the following options.

To use the Find... function in Outlook's Address Book:

1. From either the message composition window or Outlook's main screen, from the Tools menu, select Address Book....
2. Click OK to close the error messages.

   Note: You will see the above error messages each time you attempt to search the GAL by opening the Address Book.

3. If you opened the Address Book from the message composition window, go to the Advanced button in the lower left corner, and then select Find.... If you opened the Address Book from Outlook's main screen, from the Tools menu, select Find....
4. In the Find window that appears, enter your search criteria, and then click OK to search.

While composing a message:

1. Begin a new message by clicking the New button. Alternatively, from the File menu, select New, then Mail Message.
2. In the "To..." field, type the last name, a comma, and then the first name of the person to whom you wish to send a message. Then type Ctrl-k (hold down the Ctrl key and then press the letter k).
3. The name should resolve and be underlined. If there are several people with the same name, the Check Names dialog box will open with a list of matching names. Select the correct name, and click OK.

Long-term solution

To fix this problem so that you can open and search the Address Book normally, you must edit the registry to disable Outlook's address list browsing functionality. To do so:

1. From the Start menu, select Run....
2. In the "Open:" field, type regedit, and then click OK.
3. Navigate to the following key:

     HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook

4. From the Edit menu, select New, then Key.
5. Type LDAP and press Enter. This will create a new folder on the left called LDAP.
6. Select this new folder. Then, from the Edit menu, select New, and then DWORD Value.
7. Type DisableVLVBrowsing, and press Enter. This will create a new entry on the right called DisableVLVBrowsing.

   Note: Be sure to enter DisableVLVBrowsing exactly as you see it.

8. Select the DisableVLVBrowsing entry. From the Edit menu, select Modify.
9. In the Edit DWORD Value dialog box that appears, in the "Value data:" field, enter 1 (the numeral one).
10. Click OK, and then close the Registry Editor.

For more information about errors using LDAP in Outlook 2003, see article 820864 at the Microsoft Help and Support web site.