Can’t join online meeting that is created in a non-federated organization by using Lync 2013

Symptoms

Consider the following scenario:

• You deploy a proxy server that only support basic authentication in an organization. There is no DNS resolvers for Internet server in the organization.

• A Microsoft Lync 2013 user (user A) in the organization receives a meeting invitation from another user (user B). User B is in an organization that is not federated with user A’s organization.

• User A tries to join the meeting.
  
  Note To do this, user A must access Internet through the proxy server.

In this scenario, Lync 2013 keeps trying to connect to the meeting instead of prompting user A for credentials.

Resolution

To resolve this issue, install the following update:

2881070 August 2014 update for Lync 2013 (KB2881070)