You can't expand a nested contact group and Unknown is displayed in the group name in Outlook
Original KB number: 4293589
In Microsoft Outlook, you try to expand a contact group in a public folder that contains a nested contact group. However, the contact group doesn't expand, and the text <Unknown> appears at the end of the group name.
To resolve this issue, right-click the Contact folder in the Public Folder, and then select Properties. On the Outlook Address Book tab, select the Show this folder as an email address book option.
- Open the contact group, and select Update now. If there are members that can't be found, Outlook will prompt you to select one of the following options:
- Remove the lost members.
- Try to repair the lost members and remove only those that cannot be resolved.
- Cancel this operation and do not change any members.
- Select Try to repair the lost members and remove only those that cannot be resolved, and then select OK.
A similar issue occurs if another user adds a contact group from their own contacts to the public folder contact group, and then a different user tries to send an email message to that contact group. This scenario is not resolved by the Show this folder as an email address book option.