Hi Peter,
what is your version for UCCX and exchange server ?
your error is related to SMTP authentication error. you need create connector on the exchange for UCCX. the connector should use basic authentication. Also check all the permission groups, "Anonyomous user, exchange users, exchange servers, legacy exchange servers, Partners".
check the https://supportforums.cisco.com/message/4033536#4033536
HTH
Anas
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