Consider the following scenario:
You enable user A and user B for Microsoft Lync Server 2010.
User A is not a member of any Group Chat room in the environment. User B is added to a Group Chat room.
You add a distribution list (DL) as a member to a Lync Server 2010, Group Chat room. You enable this chat room to send invitations to new members.
You add both user A and user B to the DL.
Both user A and user B sign in to Group Chat.
In this scenario, user B receives the invitation but user A does not.
This issue occurs because of an automatic directory synchronization issue. The DL is not assigned a prinID. Therefore, the server does not detect the users in the DL and does not send the invitation.
Note The term DL can refer to a distribution list, security group, organizational unit and so on.
To resolve this issue, install the following cumulative update:
2670342 Description of the cumulative update for Lync Server 2010, Group Chat: February 2012