An attempt to route to an Exchange UM server failed. The attempt failed with response code %1: %2. Request Target: %3], Call ...

An attempt to route to an Exchange UM server failed.

The attempt failed with response code %1: %2.
Request Target: [%3], Call Id: [%4].
Failure occurrences: %5, since %6.
Cause: An attempt to route to an Exchange UM server failed because the UM server was unable to process the request or did not respond within the allotted time.
Resolution:
Check this server is correctly configured to point to the appropriate Exchange UM server. Also check whether the Exchange UM server is up and whether it in turn is also properly configured.