Upgrading Exchange 2016 to Exchange SE
Prerequisite Validation
Validating Your Starting Point
Before starting any major server upgrade, you must first confirm your current environment is stable and properly configured. For an upgrade from Exchange Server 2016 to the Subscription Edition (SE), this means validating your existing setup. The entire process hinges on starting from a known-good state. Neglecting this step is like building a house on a shaky foundation.
Your first task is to ensure your Exchange 2016 servers are running Cumulative Update 23 (CU23) along with the latest security updates. This is a non-negotiable baseline. The easiest way to verify this and check for other potential issues is by using the script, a PowerShell tool provided by Microsoft.
# Run this from the Exchange Management Shell
# Ensure you're in the directory where the script is saved
.\HealthChecker.ps1 -BuildHtmlReport
After running the script, open the generated HTML report. Look for any red or yellow flags that indicate configuration drift or health problems. Address all critical issues before proceeding. This script is your first line of defence against a problematic upgrade.
Understanding the Upgrade Path
You cannot perform a direct, in-place upgrade from Exchange 2016 to Exchange Server SE. The reason is a fundamental change in versioning. Exchange 2016 is major version 15.1, while Exchange 2019 and SE are major version 15.2. An in-place upgrade is only supported within the same major version. Therefore, you must perform a 'legacy' upgrade, which involves introducing new servers into your existing organisation.
The correct path requires you to introduce servers running Exchange 2019 first. You'll install servers with Exchange 2019 CU14 or a later supported version into your existing Exchange 2016 organisation. Once mailboxes and mail flow are migrated to the Exchange 2019 servers, you can decommission the old 2016 servers. Only then can you perform an in-place upgrade on your Exchange 2019 servers to Exchange SE.
Server and Hardware Requirements
Your new Exchange 2019 servers must be installed on a supported operating system. Your options are Windows Server 2019, Windows Server 2022, or the newer . Choosing a more recent OS can extend the support lifecycle of your infrastructure.
| Exchange Version | Supported Windows Server OS |
|---|---|
| Exchange Server 2019 CU14/15 | 2019, 2022, 2025 |
| Exchange Server SE | 2019, 2022, 2025 |
The hardware for these new servers must also meet specific standards, particularly if you plan to use Windows Server 2025. This OS mandates a processor made in 2017 or later and requires the server to have a [{<TPM 2.0>] chip. Beyond that, standard Exchange best practices apply. Ensure your processors support SLAT for virtualisation and AES-NI for faster encryption, as these are crucial for performance and security in a modern Exchange environment.
Always validate your hardware against both the Exchange Server and Windows Server requirements before you purchase or deploy anything.
Now that you understand the prerequisites, you are ready to check your knowledge.
What is the mandatory Cumulative Update (CU) version for Exchange Server 2016 before starting an upgrade to Exchange Server Subscription Edition (SE)?
What is the recommended first step for verifying the health and configuration of your Exchange 2016 environment before an upgrade?