Microsoft Project Online retires on 30 September; cross-tenant free/busy and calendar sharing leave EWS from 1 October

Microsoft Project Online retires on 30 September; cross-tenant free/busy and calendar sharing leave EWS from 1 October

30 September 2026 —

Not yet independently verified. This rests on Microsoft’s own Message Center posts, read through a public archive because the admin centre requires sign-in, and on Microsoft Learn; no independent report of either date was checked. We will update this when it can be confirmed, and remove this note. We will update this when it can be confirmed, and remove this note.

Two Microsoft 365 deadlines fall this week, one day apart. One ends a whole service. The other changes how calendars are shared between organisations.

Project Online: last day is 30 September 2026

Microsoft's final reminder (MC1478955, 24 September) says Project Online retires on 30 September 2026 in every cloud, including government clouds. After that date, projects and data in the service cannot be accessed. Microsoft announced the retirement in September 2025. Users who have not moved yet see an in-app banner.

The retirement covers Project Online only. The Project desktop client, Project Server and Planner are not affected. Microsoft offers three paths:

• Microsoft Planner, with its premium features under a Project Plan 3 licence, for a cloud-first work management tool;
• Project Server Subscription Edition, for organisations that want to run project management on their own servers;
• Dynamics 365 Project Operations, for organisations that tie projects to ERP.

What to do today: if anything is still in Project Online, export schedules, resource plans and reports now. Microsoft says any organisation not fully migrated should contact a Microsoft partner and its account team at once. PMO tools and reports that read Project Online data through its APIs will stop working too.

EWS deprecation starts 1 October for cross-tenant sharing

Exchange Web Services has been on notice since 2023. Microsoft Learn says EWS will be switched off in Exchange Online, and after the Midnight Blizzard incident the scope was widened to Microsoft's own apps. Message Center post MC1446796, updated on 29 September, sets the first dated step: EWS deprecation begins on 1 October 2026 for cross-tenant free/busy, MailTips (such as out-of-office notices) and calendar sharing.

These features now move to the Microsoft 365 Cross-Tenant Access Policy. Microsoft's rollout of the replacement:

• worldwide: free/busy and MailTips complete by 15 September; calendar sharing by 15 October 2026;
• GCC and GCC High: complete by 30 September;
• DoD: complete by 30 October.

Is your tenant affected? Microsoft gives two checks in Exchange Online PowerShell. If Get-OrganizationRelationship shows an enabled relationship with free/busy or MailTips access to another Microsoft 365 organisation, or Get-SharingPolicy shows an enabled policy with a calendar-sharing rule aimed at one, you need to migrate. Otherwise no action is needed. Hybrid and on-premises set-ups are out of scope.

What to do: run both checks this week. Partners in other tenants may stop seeing your availability and shared calendars if the old configuration is left in place. Set up the Cross-Tenant Access Policy with each partner organisation, and tell the teams who book cross-company meetings. The post says the tenant's own Message Center is authoritative, so compare the dates there before you act.

Sources

• Microsoft 365 Message Center MC1478955: Final reminder — Microsoft Project Online retires on September 30, 2026 (public archive) — 24 September 2026
• Microsoft 365 Message Center MC1446796: Migrate Free/Busy, MailTips, and Calendar Sharing before EWS deprecation (updated 29 September; public archive) — 29 September 2026
• Microsoft Learn: Deprecation of Exchange Web Services in Exchange Online (read 2026-09-30) — 30 September 2026