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Using Outlook, searching the Global Address List using my IMAP account, what "unavailable critical extension” mean?
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You may experience problems using Microsoft Outlook 2003 0r 2007 when browsing an LDAP serverand39s address book with more than 5,000 entries. Due to the large size of CUand39s GAL, if you are using Outlook 2003 or 2007 with an IMAP account, you may see the following error messages when you try to open the Address Book: Unavailable critical extension. After you click OK, youand39ll 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 Outlookand39s 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 youand39ll 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 Outlookand39s Address Book, follow these steps: 1. From either the message composition window or Outlookand39s 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 Outlookand39s 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, follow these steps: 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 Ctrlk 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. Longterm solution Warning: This document contains instructions for editing the registry. If you make any error while editing the registry, you can potentially cause Windows to fail or be unable to boot, requiring you to reinstall Windows. Edit the registry at your own risk. Always back up the registry before making any changes. If you do not feel comfortable editing the registry, do not attempt these instructions. Instead, seek the help of a computing support provider. To fix this problem so that you can open and search the Address Book normally, you must edit the registry to disable Outlookand39s address list browsing functionality. To do so, follow these steps: 1. From the Start menu, select Run... . 2. In the Open: field, type regedit , and then click OK. 3. Navigate to the following key: HKEYCURRENTUSERSoftwareMicrosoftOffice11.0Outlook 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 , see article 820864 in Microsoftand39s knowledge base. You can search Microsoftand39s knowledge base at: