We will be looking at migrating Exchange 2010 with Unified Messaging and Lync to 2013 in a new forest. Our current setup is two exchange 2010 servers, one running most roles (HT, MB, CAS), the other running UM. Our current domain is "domain.com" and will be changing this to "corp.newdomain.com". The domain name change is for business purposes and unfortunately has to happen. My process looks like as follows: Build up new corp.newdomain.com domain.Build New Exchange 2013 Servers, 2 CAS, 2 DAG (for failover)Build New Lync 2013 server After that, I'm not sure of what I need to do. From looking over documentation http://technet.microsoft.com/en-us/library/bb124734(v=exchg.150).aspx it looks like I need to install 2013 in the old forest and then use the cross-forest migration to move all the users to the new forest. My question is, can I skip installing 2013 in the old forest and just migrate the users to the new 2013 forest? Also, does anyone know what I need to worrry about with Lync and this type of migration?

Hello, You don't need to install Exchange 2013 in the old forest. If you have two forest, you need to: Enable Trust Configure ADMT and move users Prepare to move mailbox Move mailbox cross forest Use this guide to move mailbox cross forest, http://technet.microsoft.com/en-us/library/ee633491(v=exchg.150).aspx Eli. Unified Communication , https://www.facebook.com/groups/mucugi/