💡 Our Technical Review in summary
Summary
- Message ID: MC1125491 (Updated October 28, 2025).
- Feature: Users of the new Microsoft Outlook for Windows will soon have the ability to add file attachments to draft emails while working offline.
- Functionality: Emails drafted with attachments during offline sessions will be stored locally and sent automatically once the device establishes an internet connection.
- Timeline: Targeted Release begins late October 2025. General Availability (Worldwide) starts early January 2026 and is expected to complete by early February 2026. GCC rollout is scheduled for mid-to-late February 2026.
Impact
- User Productivity: This update closes a functional gap in the new Outlook, allowing mobile or remote workers to complete full email drafts without needing an active connection.
- Default Configuration: The feature is governed by the existing
OWAMailboxPolicy-OfflineEnabledWinpolicy. If offline mode is already enabled for your organization, this functionality will be available by default. - Client Requirement: This update applies specifically to the new Outlook for Windows; it does not change the behavior of the classic Outlook desktop application.
- Data Handling: Attachments added offline are stored in the local cache until synchronization occurs.
Action Required
- Review Policies: Use the
Get-OwaMailboxPolicyandSet-OwaMailboxPolicyPowerShell cmdlets to verify or modify theOfflineEnabledWinsetting for your users. - User Configuration: For the feature to work, users must ensure that “Enable offline email, calendar, and people” and “Include file attachments” are toggled ON under Settings > General > Offline in their Outlook client.
- Update Documentation: Update internal help desk guides and training materials to reflect the new offline attachment capabilities and the updated rollout dates (January/February 2026).
- Compliance Review: While no specific compliance considerations were identified by Microsoft, organizations with strict data loss prevention (DLP) or local storage policies should review how offline attachments align with their security standards.
Microsoft Official Update
Service: N/A
Category: stayInformed
Severity: normal
Updated October 28, 2025: 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 November 2025.
- General Availability (Worldwide): Rollout begins in early January 2026 (previously mid-December 2025) and is expected to complete by early February 2026 (previously early January 2026).
- General Availability (GCC): Rollout begins in mid-February 2026 (previously mid-January 2026) and is expected to complete by late February 2026 (previously late January 2026).
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
Compliance considerations
No compliance considerations identified, review as appropriate for your organization.
