We currently have a single forest with multiple domains. Each domain is currently running Microsoft Exchange Server 2010 setup with two mailbox servers and two CAS/HUB transport servers. One of our sites is planning on migrating to Microsoft Exchange Server 2013; however, not all of our other sites have the latest service pack and cumulative update. Are there any issues with updating the AD Schema when a Exchange 2010 server is not at the latest service pack and CU? Should I have the other site install the latest SP and CU before updating the schema?