This article describes an update that enables Microsoft Lync 2010 users to join a meeting when proxy authentication is required.

Consider the following scenario:

  • You sign in to Lync 2010 in an organization that has a proxy server deployed.

  • The proxy server requires all outgoing Web access requests to be authenticated.

  • A Lync 2010 user who is not in a federated organization sends you a meeting invitation. The invitation enables anonymous users to join the meeting.

  • You try to join the meeting.

In this scenario, a 407 error is returned form the proxy server. Additionally, you receive the following error message:

Cannot sign in because the server is temporarily unavailable.

error ID 28 (source ID 238).

Note After this update is installed you will be prompted to type in credentials when you try to join a meeting.

To enable users to join meetings when proxy authentication is required, apply the following update:

2791382 Description of the cumulative update package for Lync 2010: March 2013

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