Windows 10 & Exchange Server: Get Ready for October 2025 End-of-Life

There are three (3) options available to organizations.  

Option 1: Exchange Online 

Primarily, the most common path forward will be to migrate your email server to Exchange Online provided through a Microsoft 365 subscription. This is a tried and tested solution that many organizations have executed in recent years. Migrating to Exchange Online brings a host of benefits, including: 

• Cost Savings: Migrating to Exchange Online allows an organization to reduce infrastructure and maintenance costs by moving the management of the underlying infrastructure to Microsoft’s responsibility.  

• Simplified Licensing: Outside of additional licensed features for Microsoft 365 in general, licensing Exchange Online for email is straightforward. By having an Exchange Online license as a standalone or having it bundled into another license (Business Premium / Enterprise), you immediately have access to the mailbox.  

• Reliability and Uptime: Migrating your Exchange Server to Exchange Online means your email platform is now hosted within a Geo-redundant datacenter, relieving you from a single point of failure tied to your existing Internet Service Provider.  

• Scalability: As your organization grows, the Exchange Online tenant grows. Adding new users to the tenant is as simple as creating an account and assigning an appropriate license.  

Option 2: Exchange Server SE 

The second option available to organizations will be to upgrade their existing Exchange Server 2016 / 2019 installation to Microsoft Exchange Server Subscription Edition (SE). Exchange Server SE is the soon-to-be-released version of the local Microsoft Exchange Server. Microsoft has decided to change the naming convention of the platform by excluding the year of release. If your organization has requirements or application limitations that require you to keep your Exchange server on-premises, Microsoft is trying to streamline the upgrade process.  

Initially, the upgrade to Exchange Server SE will be offered as a cumulative update (CU) from the current release of Exchange Server 2019 (CU15). Cumulative Updates are a bundle of features and bug fixes that Microsoft releases periodically. In this instance, rather than going to CU16, the update this summer will upgrade the Exchange Server to the newly released SE version.  

If you are on Exchange Server 2019 CU14 or lower, or Exchange Server 2016, you will need to upgrade your server to Exchange Server 2019 CU15 to receive the update to Exchange Server SE. There is no direct update from any other version of Exchange other than Exchange Server 2019 CU15.  

Additionally, you will need to address licensing concerns when upgrading to Exchange Server SE. Here are common licensing scenarios for SE: 

• If you are currently licensed for Exchange Server 2019 and you have an active Software Assurance (SA) agreement with Microsoft, you are ready to go for Exchange Server SE. This licensing scenario allows for a direct upgrade to SE at no additional cost other than maintaining your Software Assurance subscription.  

• License your local Exchange Mailboxes through a Microsoft 365 Enterprise subscription. This is the same licensing bundle available if you were migrating to Exchange Online. With the Enterprise licensing bundle, Microsoft allows the extension of local use rights to maintain a local Exchange Server. This is useful for organizations that may need to deploy a Hybrid model where some of their infrastructure resides in Exchange Online and some in on-premises Exchange Server SE.  

• Purchase new Exchange Server 2019 Licensing with Software Assurance and the appreciate Client Access Licenses (CALs). This one can be a hard pill to swallow for organizations that have existing Exchange Server 2019 Licensing but no Software Assurance subscription. You can only buy SA in a short time window at the original time of purchase. Since Exchange Server SE Licensing is not currently being sold (Will arrive later this year), organizations are only able to buy Exchange Server 2019 with Software Assurance today to prep for the upcoming upgrade,  

Option 3: Status Quo 

Due to a variety of circumstances, many organizations will choose to forgo Option 1 and Option 2 and leave their legacy Exchange Server running as is past the End-of-Life date in October. While we would never recommend this option, it is available to your organization. Note that this does carry associated risks that you will need to weigh against the cost of upgrading the infrastructure.  

• Vulnerabilities: Microsoft will no longer be releasing security updates for these platforms. It is typical of malicious attackers to hold on to known vulnerabilities and not actively target systems that are in the final months of support, knowing that Microsoft will not be releasing security patches anymore. This leaves your server as a target for threat actors.  

• Business Continuity: Should your Exchange Server experience a catastrophic failure of some kind, Microsoft Support will not provide assistance in recovery, leaving you working with your IT team to resolve the issue, which in some cases may not be possible given the severity of the failure.  

• Compliance: Many cybersecurity frameworks and compliance standards (NIST, ISO, FINRA, HIPAA) require organizations to maintain their infrastructure and keep their systems in a supported state. By running an operating system or core application that is no longer supported, your organization runs the risk of failing to meet a compliance standard.