Friday, November 25, 2011

Calls cannot be established to UM for external users

I have faced a problem when integrating Lync with Exchange 2010 UM , where calls could not be established to UM for external users, whenever i call the susbscriber access from the Internet i get the following error:
"call failed due to network issues. try logging out of lync logging back in, or try again later"
After revewing the logs, i found the following entry in the event viewer on the Lync front-end server :

Event ID: 1400 Source: MSExchange Unified Messaging

The following UM IP gateways did not respond as expected to a SIP OPTIONS request.

Transport = TLS, Address =, Port = 5061, Response Code = 0, Message = This operation has timed out.
Issue a certificate dedicated to UM, where the subject name is the FQDN of the UM server.

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