MC1125491 – M365 Change Digest

One-line summary

Users of the new Outlook for Windows can attach files to draft emails while offline; rollout begins April 2026 for general availability and respects existing admin policy settings.

Similar updates

Details

RoadmapIds

496371

Summary

Microsoft Outlook for Windows will allow users to add file attachments to emails while offline, sending them automatically once reconnected. Rollout is delayed to late March 2026 for Targeted Release and April-May 2026 for General Availability. Offline settings and policies control this feature.

Platforms

Desktop

Body (from Message Center)

Updated March 9, 2026: We have updated the timeline. Thank you for your patience.

Introduction

We’re enhancing offline functionality in the new Microsoft Outlook for Windows. This update (Microsoft 365 Roadmap ID 496371) enables users to add file attachments while composing emails offline, improving productivity for those working without an internet connection.

When this will happen

Targeted Release (Worldwide): Rollout begins in late October 2025 and is expected to complete by late March 2026 (previously late November 2025).
General Availability (Worldwide): Rollout begins in early April 2026 (previously early January) and is expected to complete by late April 2026 (previously early February).
General Availability (GCC): Rollout begins in early May 2026 (previously mid-February) and is expected to complete by late May 2026 (previously late February).

How this affects your organization

Users with offline mode enabled in the new Outlook for Windows will be able to attach files to draft emails while offline. These emails, including attachments, will be sent automatically once the device reconnects to the internet.

This feature will be on or off by default based on your current configuration of the OWAMailboxPolicy-OfflineEnabledWin policy. No changes will be made to existing configurations.

What you can do to prepare

To enable this functionality, ensure the following settings are configured in the new Outlook under Settings > General > Offline:

Enable offline email, calendar, and people
Include file attachments

Admins can manage this feature using the OWAMailboxPolicy-OfflineEnabledWin mailbox policy. Learn more at Set-OwaMailboxPolicy.

Caption i. Offline editing can be enabled or disabled in Settings > General > Offline

Screenshot highlighting toggle to Enable offline email, calendar, and people.

Compliance considerations

No compliance considerations identified, review as appropriate for your organization.

Raw JSON (for debugging)

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{
  "snapshot_item": {
    "action_required_by": null,
    "ai_action_required_by": "2026-01-01T00:00:00Z",
    "ai_actions": [
      "Review and adjust OWAMailboxPolicy-OfflineEnabledWin as needed",
      "Inform users about new offline attachment capability"
    ],
    "ai_master_tags": [
      "User",
      "Admin"
    ],
    "ai_model": "gpt-4.1",
    "ai_summary": "Users of the new Outlook for Windows can attach files to draft emails while offline; rollout begins April 2026 for general availability and respects existing admin policy settings.",
    "ai_topics": [
      "Exchange",
      "Microsoft 365 Apps",
      "Outlook"
    ],
    "category": "stayInformed",
    "details_map": {
      "Platforms": "Desktop",
      "RoadmapIds": "496371",
      "Summary": "Microsoft Outlook for Windows will allow users to add file attachments to emails while offline, sending them automatically once reconnected. Rollout is delayed to late March 2026 for Targeted Release and April-May 2026 for General Availability. Offline settings and policies control this feature."
    },
    "id": "MC1125491",
    "importance": 4,
    "is_major_change": false,
    "last_modified": "2026-03-09T17:34:05Z",
    "ms_products": [
      "Exchange",
      "Microsoft 365 Apps"
    ],
    "platforms": "Desktop",
    "roadmap_ids": [
      "496371"
    ],
    "services": [
      "Exchange Online",
      "Microsoft 365 apps"
    ],
    "severity": "normal",
    "tags": [
      "Updated message",
      "New feature"
    ],
    "title": "(Updated) Microsoft Outlook for Windows: Add attachments while offline"
  }
}