Lync Phone Edition for Aries telephones does not connect to Exchange Web Service through an HTTP proxy server

Symptoms

Consider the following scenario:

• You deploy an on-premise Microsoft Lync Server 2010 or Microsoft Lync Server 2013 environment for an organization.

• Mailboxes of users in the organization are hosted on Exchange Online.

• There is no routing from an internal network to the Internet.

• Lync Phone Edition for Aries telephones download and interpret a proxy auto-config (PAC) file.

In this scenario, Lync Phone Edition for Aries telephones only tries to directly connect to Exchange Web Service.

Cause

This issue occurs because an important error that occurs when the direct connection to Exchange Web Service fails does not trigger the use of the proxy connection.

Resolution

To resolve this issue, install one of the following cumulative updates:

• May 2015 cumulative update for Microsoft Lync Phone Edition for Aastra 6721ip and Aastra 6725ip telephones

• May 2015 cumulativeupdatefor Microsoft Lync Phone Edition for HP 4110 and HP 4120

• May 2015 cumulative update for Microsoft Lync Phone Edition for PolycomCX500, Polycom CX600 and Polycom CX3000 telephones