Microsoft 365 planning calendar

Microsoft changes. A clear plan for what comes next.

See what changes, who may be affected and where to start. A practical calendar for October 2026 to April 2027.

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Four milestones to plan around

Match each change to the systems you actually use.

  1. 1 October 2026Phased disablement

    Check applications that still use EWS

    Exchange Online starts disabling Exchange Web Services (EWS). An application's behavior depends on the tenant's EWS settings and allowed app IDs.

    Your next step: Inventory internal and vendor applications, confirm their migration plans, and review your tenant configuration before the rollout.

    Plan the remediation scope

    Identify EWS dependencies, agree the supported replacement for each app, and define a pilot and rollback plan.

    System counts, application complexity and validation requirements determine the agreed scope.

    Explore Microsoft 365 migration
    Microsoft Learn: EWS retirement timeline
  2. Before 3 November 2026Preview ending

    Replace memberOf rules before updates stop

    After 3 November, dynamic groups, dynamic administrative units and entitlement auto-assignment policies using the memberOf operator stop updating and keep their last known state.

    Your next step: Find affected rules, choose supported logic or assigned membership, and validate membership and access after the change.

    Plan the remediation scope

    Inventory affected configurations, agree replacement rules, and test expected access with an approved change plan.

    System counts, application complexity and validation requirements determine the agreed scope.

    Explore identity and Zero Trust
    Microsoft Learn: memberOf preview ending
  3. End of December 2026Default changes

    Modernize apps and devices that send email

    SMTP AUTH Basic authentication is scheduled to be disabled by default for existing tenants. This is not its final removal date; Microsoft says administrators can still enable it if needed.

    Your next step: Identify affected applications and devices. Validate OAuth or another supported sending method before changing the production configuration.

    Plan the remediation scope

    Inventory senders, agree the supported mail path, and test delivery and recovery with approved synthetic messages.

    System counts, application complexity and validation requirements determine the agreed scope.

    Explore application and workflow modernization
    Microsoft Exchange Team: updated SMTP AUTH timeline
  4. 1 April 2027Permanent retirement

    Finish the move away from Exchange Online EWS

    EWS is scheduled to be fully and permanently disabled in Exchange Online. This retirement does not apply to on-premises Exchange Server.

    Your next step: Complete app migrations and vendor upgrades, verify replacement features, and retire remaining Exchange Online EWS dependencies.

    Plan the remediation scope

    Validate replacement workflows, collect acceptance evidence, and remove EWS dependencies under an agreed cutover plan.

    System counts, application complexity and validation requirements determine the agreed scope.

    Explore Microsoft 365 migration
    Microsoft Learn: Exchange Online EWS deprecation

Also check: external sharing

Guest sharing: check your tenant's rollout

SharePoint and OneDrive guest authentication is moving to Microsoft Entra B2B. One-time passcodes remain available through Entra B2B.

Your next step: Check guests who used the older SharePoint passcode flow and verify that they have the appropriate Entra B2B guest account and access.

Timing and remediation guidance

The current Microsoft Learn FAQ says affected guests without an Entra B2B account can see access denied starting July 2026. Confirm the schedule in your tenant's Message Center; an October deadline is not confirmed by that FAQ.

Review affected external sharing, guest identities and access policies, then agree and validate the remediation.

Explore guest access and identity services
Microsoft Learn: SharePoint and Entra B2B FAQ

Turn the calendar into a plan

Know which changes need your attention.

Share the affected systems and your target date. We will agree the assessment and remediation scope before work begins.

Discuss your priorities

Questions before you start

Does every deadline affect every organization?

No. The impact depends on the applications, authentication methods and rules your organization uses. Start with an inventory and your tenant's Microsoft Message Center notices.

Are one-time passcodes disappearing?

No. Microsoft says guest authentication is moving from SharePoint's older flow to Entra B2B, where one-time passcodes remain supported. Check guest identities and access rather than disabling passcodes.

Is SMTP AUTH Basic authentication permanently removed in December?

No. Microsoft's current announcement describes a default disablement at the end of December 2026. It says the final removal date will be announced in the second half of 2027.

What happens when I ask for help?

Use our existing Contact page to describe the affected systems and your target date. We review the request and agree the scope, prerequisites and next step before any implementation. Please do not send credentials or sensitive customer data.

This calendar is planning guidance. Microsoft can update schedules, and tenant or cloud-specific notices may differ. Check the linked sources and your Message Center before approving changes.