Life-Shortening Events for Exchange Server SE

Customers should not expect SE software to keep all its features or continue to work with other Microsoft products through 2035. (See accompanying graphic.)

Coexistence cut off with older versions. Per Microsoft’s plans, Exchange Server SE Cumulative Update 2 (CU2), due in the second half of 2026, will not install in an Exchange organization that includes Exchange Server 2013, 2016, 2019, or other older versions. Going without CU2 for a long period could have several bad effects. For example, Exchange Online may block servers without CU2 as “persistently vulnerable” if they lack security fixes delivered by CU2. Also, Microsoft’s support team may choose to suspend work on a customer’s problem until the customer has reproduced it on CU2, or whatever CU is the most recent at the time.

Classic Outlook retiring. A “new Outlook” app will replace the current “classic Outlook” on Windows according to Microsoft’s current plans. New Outlook treats Exchange Server SE as a generic Internet (IMAP) e-mail server, eliminating Exchange-specific mail features. Customers will be able to get classic Outlook through at least 2029, but it might not be available and supported through 2035.