We have not attempted Exchange 2013 yet, but perhaps our configuration for Exchange 2010 will help.
Ensure that your CA IM Connector Server is installed on a server in the same AD forest as your Exchange server.
Ensure that you have the Exchange Management Tools installed. It's a good idea to try creating a mailbox manually through the Exchange Management Console before trying it through CA IM. Use the instructions included in the CA Wiki to run a test Powershell command against the Exchange Server to confirm that you can communicate and authenticate.
Environment Variables
ADS_AGENTLESS_AUTHMETHOD=2
ADS_AGENTLESS_LOGLEVEL=3
ADS_AGENTLESS_MAXCONN=5
ADS_AGENTLESS_MODE=1
Endpoint
Create your AD endpoint. Ensure that the credentials you use in the endpoint configuration have authority to read the schema in AD. (Organizations with highly distributed support roles and responsibilities often lock down portions of the schema, which can cause problems.) Once you have your endpoint configured, perform an Explore so the CA IM Provisioning Directory can discover the Exchange Server attributes in AD. Consider using Provisioning Manager to attempt a manual mailbox create so you can confirm your connectivity to the Exchange Server. Create / update your AD Account Template so it includes the Exchange attributes you desire, then attempt to apply that template to a user.