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What Microsoft’s Period 2 ESU covers
Microsoft announced Period 2 on April 15, 2026, for customers still completing migration from eligible Skype for Business and Exchange Server deployments. The coverage window runs from May through October 2026, and Microsoft has announced no period after October.
Purchases made for Exchange on or after April 15, 2026 are treated as Period 2 purchases. Holding Period 1 does not enroll an organization automatically, so a new contract is required for the May–October window.
Exchange Server requirements
Exchange Period 2 is planned for the following cumulative-update baselines:
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| Product | Qualifying baseline | Coverage window | Update delivery |
|---|---|---|---|
| Exchange Server 2016 | CU23 | May–October 2026 | Required security updates supplied privately to ESU customers |
| Exchange Server 2019 | CU14 or CU15 | May–October 2026 | Required security updates supplied privately to ESU customers |
The program is aimed at Microsoft Enterprise Agreement customers that cannot finish moving to Exchange Subscription Edition (SE) before the end of April 2026 but still need coverage for Critical and Important security changes. Microsoft has not published a public Period 2 price or self-service checkout in its announcement; eligible organizations must obtain purchase details from their Microsoft account team.
Skype for Business Server requirements
Organizations running Skype for Business Server 2015 or 2019 need a separately purchased Period 2 ESU contract for May through October 2026. The original ESU arrangement covered those versions after their support ended, with October 14, 2025 cited as the original end-of-support date.
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Microsoft continues to direct customers toward Skype for Business SE rather than treating ESU as a long-term operating plan. The public announcement does not provide a complete SKU, price list, or self-service enrollment process for the Skype Period 2 contract, so account-team confirmation is required.
ESU does not mean a monthly security release
Period 2 is conditional coverage, not a guaranteed patch cadence. Microsoft says it will release an update only when it determines that a Critical or Important security change requires one, and it is not committing to release a security update every month. Customers are told on Patch Tuesday whether an update is available.
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What happened in August 2026
Microsoft’s August 2026 Skype notice reported no security release for any Skype for Business Server version, including customers with Skype for Business 2015/2019 ESU and Skype for Business SE. Microsoft said it would continue making an explicit announcement through the end of Period 2 even when no update is issued.
For Exchange, the August security-update notice directed ESU customers to Microsoft’s Security Update Guide for CVE information. Access questions were directed to ExchangeAndSfBServerESUInquiry@service.microsoft.com.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.ESU or Subscription Edition?
ESU buys time; Subscription Edition is Microsoft’s recommended durable destination. Use the following decision points before committing funds:
| Decision factor | Period 2 ESU | Subscription Edition migration |
|---|---|---|
| Eligibility and contracting | Requires a qualifying agreement and a separately purchased Period 2 contract; Exchange purchase information comes through the Microsoft account team. | Requires planning and licensing for the target SE deployment rather than a temporary ESU enrollment. |
| Time horizon | Ends October 31, 2026, with no further extension announced. | Designed as the continuing platform after the legacy-server transition. |
| Security coverage | Only Critical or Important changes that Microsoft determines require an ESU release; no monthly guarantee. | Moves the organization onto the supported edition instead of relying on a finite exception program. |
| Technical baseline | Exchange must be on 2016 CU23 or 2019 CU14/CU15; Skype coverage applies to Server 2015/2019 customers that purchase the period. | Requires a migration plan, testing, and operational readiness for the SE target. |
| Operational effort | Lower immediate change, but the organization must still complete migration before the program ends. | Higher near-term project effort, with the benefit of removing the legacy-version deadline. |
Choose ESU only when migration cannot be completed by the deadline and the organization can meet the contract and version conditions. Treat the six months as a controlled migration buffer, not as permission to defer the project indefinitely.
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Practical steps for organizations considering Period 2
- Inventory the servers. Record every Exchange and Skype for Business server, edition, cumulative-update level, and dependency. Confirm that Exchange systems meet CU23 for 2016 or CU14/CU15 for 2019.
- Validate commercial eligibility. Ask the Microsoft account team whether the organization’s Enterprise Agreement and deployment qualify, and request the Period 2 contract terms. Do not assume Period 1 enrollment carries forward.
- Set the security expectation. Build patch operations around Microsoft’s Patch Tuesday notices and Critical/Important criteria, not a promised monthly ESU package.
- Track Microsoft notices. Review the Security Update Guide for Exchange CVEs and the Skype for Business Server announcements, including explicit “no release” notices.
- Maintain the SE migration plan. Set a date, test integrations and authentication, assign owners, and leave contingency time before October 31, 2026. Microsoft’s Skype guidance specifically asks customers to keep upgrading to Skype for Business SE.
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