Microsoft kicks off phase 2 of paid ESU program for some legacy software

Mainstream support for Skype for Business (SfB) Server and Exchange 2016/2019 ended in October 2025, but many customers were still actively using this product and could not migrate to newer versions for multiple reasons. To continue offering support to them, Microsoft announced a paid Extended Security Update (ESU) program. Now, the first phase of this program has ended, and customers have the option to purchase the second phase.

Period 1 of the ESU program for both these software suites began in October 2025 and is scheduled to end at the start of May 2026. As such, customers can now begin to purchase ESUs for Period 2. Any ESU purchase that they make from today will be considered a purchase for Period 2 and give them six months of extended support, going up until October 2026. Even if you purchased Period 1, you will need to purchase Period 2 separately, as you will not be automatically enrolled into the latest ESU. You do not need to purchase Period 1 prior to purchasing Period 2.

Just like the existing ESU phase, updates for Period 2 won't be made available publicly. Instead, Microsoft will privately explain to your organization how you can continue receiving security updates.

Speaking of which, it's worth highlighting that ESU customers only receive security updates that patch important or critical vulnerabilities. Updates are not guaranteed, so you could theoretically go on six months without an update, although you paid for Period 2.

Microsoft has emphasized that Period 2 is not an extension of Period 1, and is just meant to support customers as they plan their migrations to more modern support versions of Exchange Server and SfB Server; it claims that it would rather not sell any Period 2 ESUs at all. Do keep in mind that the latest ESUs are not available automatically in Volume Licensing or Software Assurance, and can only be purchased by commercial entities with a Microsoft Enterprise Agreement (EA).