Microsoft’s Extended Security Update (ESU) programs offer a temporary, paid security-update bridge for organizations still running Exchange Server 2016 or 2019, or Skype for Business Server 2015 or 2019. ESU does not extend lifecycle support or restore ordinary product support. Microsoft’s recommended destination is the corresponding Subscription Edition.
As of Microsoft’s April 15, 2026 Exchange announcement and the updated Skype for Business notice, Period 2 covers May through October 2026 and must be purchased separately. Microsoft says Exchange ESU will not be extended beyond that period.
Which servers are covered, and for how long?
Microsoft announced the initial six-month programs on July 15, 2025. The Exchange offer covers Exchange Server 2016 and 2019; the Skype for Business offer covers Skype for Business Server 2015 and 2019. They are separate programs with distinct eligibility and purchasing arrangements—not one shared entitlement.
| Program | Products and versions | Period 2 coverage | Purchase and migration destination |
|---|---|---|---|
| Exchange ESU | Exchange Server 2016 CU23 and Exchange Server 2019 CU14 or CU15 are the versions Microsoft specified for planned Period 2 updates. | May through October 2026 | Purchase Period 2 separately, even if enrolled in Period 1. Microsoft recommends Exchange Server Subscription Edition. |
| Skype for Business ESU | Skype for Business Server 2015 and 2019 are covered by the announced program. The cited Period 2 notice does not state a cumulative-update eligibility list. | May through October 2026 | Purchase Period 2 separately. Microsoft recommends Skype for Business Server Subscription Edition. |
Microsoft’s Exchange announcement says there will be no further Exchange ESU extensions after Period 2. The Skype for Business notice describes Period 2 through October 2026; it does not establish a later coverage period. Check with your Microsoft account team for current eligibility and purchasing status before making plans, since coverage depends on the applicable program and customer arrangements. Exchange ESU announcement; Exchange Period 2 announcement; Skype for Business ESU announcement.
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What ESU provides—and what it does not
During the applicable coverage period, ESU provides access to Critical and Important security updates Microsoft may release for eligible systems. It is a limited security-update benefit, not a continuation of normal product support.
- Lifecycle support does not resume. The servers remain out of support.
- Ordinary support cases are not included. Microsoft says an exception may apply when a case is directly related to an update issued to ESU customers during the ESU period.
- Updates are limited to the eligible program and period. ESU is not a promise of indefinite updates or an extension beyond the stated coverage.
How to get ESU
Microsoft directs customers to their Microsoft account team for program eligibility, purchasing details, and delivery information. The Exchange announcement says the account team can provide per-server cost; Microsoft does not publish a universal price in the announcement. Do not assume that a particular deployment or contract qualifies.
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- Identify the server family and exact version or cumulative update in use. For Exchange Period 2, Microsoft specifies Exchange 2016 CU23 and Exchange 2019 CU14/CU15.
- Contact your Microsoft account team to confirm eligibility, cost, purchasing terms, and how updates are delivered for your organization.
- If you need coverage after Period 1, ask about Period 2 explicitly. Microsoft states that Exchange Period 2 requires a separate purchase, and the Skype for Business notice likewise says Period 2 must be purchased separately.
- Plan and execute migration to the relevant Subscription Edition rather than treating ESU as a long-term operating plan.
What organizations should do next
If you run Exchange Server 2016 or 2019
Confirm your cumulative update and whether your organization has purchased the applicable period. For Period 2, the specified versions are Exchange 2016 CU23 and Exchange 2019 CU14/CU15. Microsoft’s stated migration destination is Exchange Server Subscription Edition. The December 2025 Exchange security-update announcement provides additional context on later update eligibility: Released: December 2025 Exchange Server Security Updates.
If you run Skype for Business Server 2015 or 2019
Ask your Microsoft account team to confirm your ESU eligibility and Period 2 purchase requirements; do not assume Exchange’s version-specific criteria apply. Microsoft recommends migration to Skype for Business Server Subscription Edition.
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