Exchange 2013 Gets New Update Model

The update release policy for Exchange Server has changed from a rollup update (RU) model to a Cumulative Update (CU) model with Exchange 2013. CUs are delivered approximately quarterly; CU1 arrived in Apr. 2013, CU2 in July 2013, and CU3 in Nov. 2013. Security updates are delivered separately from CUs on an as-needed basis since these fixes can be time critical. The new update model delivers more predictable updates and keeps the on-premises Exchange product in better synchronization with Exchange Online.

CUs contain the full product, although a CU can be applied to an existing installation. Security updates will be cumulative between CUs, so only the most recent security update release after a CU need be applied. CUs contain all previous CUs and security updates.

Customers are not required to install CUs to be eligible for product support, but Microsoft will direct customers to install a CU if it is expected to fix their issues. However, customers who have implemented hybrid configurations with Exchange Online or who are using Exchange Online Archiving must update installations to the latest CU.