In Microsoft Outlook 2010, when you try to open a hidden mailbox user's shared folder by using his or her LegacyExchangeDN attribute, the Check Names dialog box appears together with the following message:
Microsoft Outlook does not recognize "legDN".
In this message, legDN is a placeholder for the LegacyExchangeDN value that you typed in the Open Other User's Folder dialog box.
The recipient is hidden from the global address list (GAL), and this causes the behavior that is mentioned in the "Symptoms" section. Microsoft Exchange Server 2010 provides this functionality to prevent a recipient alias from being made public. This functionality may be enabled for security reasons. Additionally, an Exchange Administrator may want to prevent resource recipients from accidentally being used by a large group of users. If an Outlook user is using the Offline Address Book (OAB), the user cannot access a hidden user's shared folders. This is the case even if the user has permission to view the folders.
When a recipient is hidden from the GAL, the recipient is not included in the OAB when the Exchange server generates the OAB. If an Outlook client has Cached Exchange Mode enabled, the recipient is not listed in the OAB. Therefore, the typical methods to access a shared folder do not let a user select a hidden user from the OAB.
To resolve this issue, you must install an Exchange Server 2010 update rollup and an Outlook 2010 hotfix package. These two product updates work together to enable the LegacyExchangeDN (legdn) value for the hidden user to be used to open shared folders.
To enable the LegacyExchangeDN (legdn) value in this scenario, follow these steps:
Install the Exchange Server 2010 update. To do this, apply the following update:
2685289 Description of Update Rollup 3 for Exchange Server 2010 Service Pack 2
Install the Outlook 2010 update. To do this, apply the following update:
2687351 Description of the Outlook 2010 hotfix package (Outlook-x-none.msp): August 28, 2012
After you install both updates, you can use Outlook 2010 to open the shared folders of a hidden mailbox. To do this, follow these steps:
In Outlook 2010, click the File tab on the Ribbon, and then click Open.
Click Other User's Folder.
This opens the Open Other User's Folder dialog box, as shown in the following screen shot. Type the LegacyExchangeDN value for the hidden mailbox from which to open a shared folder.
Note To open the shared folder of a hidden recipient, you must provide the LegacyExchangeDN value for the hidden user. This attribute value can be obtained from your Exchange Server administrator. Outlook recognizes the entry as a LegacyExchangeDN and resolves the entry against the GAL and not against the OAB.
Important This is the only dialog box in which the LegacyExchangeDN value can be used to open a hidden user's shared folders from. You cannot use the calendar module dialog boxes to open a shared calendar from an Exchange recipient that is hidden from the GAL.
For more information about the Exchange server update, click the following article number to view the article in the Microsoft Knowledge Base:
2670099 Outlook cannot resolve the LegacyExchangeDN of hidden mailboxes in an Exchange Server 2010 environment