Offline Calendar Support in the New Outlook for Windows

Microsoft is expanding offline capabilities in the new Outlook for Windows, making the app more reliable for users who work in low-connectivity or no-connectivity environments.

Starting later this year, users will be able to create, edit, and delete single calendar events while offline. Once the device reconnects, all changes will automatically sync to the cloud.

This enhancement is a step forward in Microsoft’s broader effort to make Outlook a true “work anywhere” too

Rollout Timeline

• Targeted Release: Begins late September 2025, completing by late October 2025.
• General Availability (Worldwide): Begins late October 2025 (updated from mid-September) and completes by mid-December 2025 (updated from mid-October).

With this update, users who have offline mode enabled in the new Outlook for Windows will be able to:

• Create new single calendar events without internet access.
• Edit or delete existing calendar events that were previously synchronized within the offline timeframe set in Outlook.

Important limitation: Offline support currently applies only to single events. Recurring events (series) are not yet supported.

How It Works

The feature is controlled by the existing OWA Mailbox Policy setting:

• OWAMailboxPolicy -OfflineEnabledWin

  • If set to True: offline calendar functionality is available.

  • If set to False: offline calendar functionality is disabled.

  • Default policy values remain unchanged by this update.

Admins can configure this using the Set-OwaMailboxPolicy cmdlet.

At the user level, offline mode can be enabled in Outlook under:

• Settings > General > Offline

  • Enable offline email, calendar, and people

Here are a few steps admins should take ahead of rollout:

1. Review mailbox policies – Confirm whether OfflineEnabledWin is enabled for the users who need offline calendar access.

2. Communicate to users – Let them know what is and isn’t possible offline (single events only, no recurring events).

3. Encourage pilot testing – Start with users in Targeted Release to gather feedback and identify issues early.

Final Thoughts

Outlook Calendar is at the center of daily productivity. By extending offline capabilities to cover event creation, editing, and deletion, Microsoft is closing a long-standing gap for users who work beyond reliable connectivity.

This may seem like a small step, but for frequent travelers, remote workers, and field teams, it’s a significant improvement in how Outlook supports real-world productivity.

As with most updates, the key to smooth adoption is preparation. Ensure offline mode is enabled where needed, update mailbox policies if required, and keep users informed. By rollout completion in December, your organization can be fully ready to take advantage of this enhancement.