Introduction
We are introducing a new OWAMailboxPolicy setting that allows administrators to control whether file attachments are available when users work offline in the new Outlook for Windows. This change adds a tenant-level configuration option for managing offline attachment access while preserving existing offline policy behavior by default.
When this will happen:
The new policy will rollout mid-April 2026
How this affects your organization:
Who is affected:
- Exchange Online administrators
- Users of the new Outlook for Windows who use Offline mode
What will happen:
- A new
OWAMailboxPolicy setting named AttachmentsOfflineEnabledWin becomes available.
- The policy is enabled by default (
$true).
- Administrators can allow or block access to file attachments while working offline in the new Outlook for Windows.
- This change does not affect the existing configuration of
OfflineEnabledWin.
- If
OfflineEnabledWin is set to $false, offline file attachments remain disabled even if AttachmentsOfflineEnabledWin is set to $true.
| OfflineEnabledWin |
AttachmentsOfflineEnabledWin |
Offline mail available? |
Offline attachments available? |
Description |
| true |
true |
Yes |
Yes |
Offline mode is enabled. Users can work offline and access file attachments. |
| true |
false |
Yes |
No |
Offline mode is enabled, but file attachments are not accessible while offline. |
| false |
true |
No |
No |
Offline mode is disabled. File attachments are also not available while offline. |
| false |
false |
No |
No |
Offline mode is fully disabled. No offline mail or attachments are available. |
What you can do to prepare:
- No action is required if the default behavior meets your organization’s requirements.
- Review your existing
OfflineEnabledWin policy configuration.
- Configure
AttachmentsOfflineEnabledWin at the tenant level if you want to control offline attachment access.
- Communicate any changes to helpdesk or security teams.
Learn more and configure the policy using Exchange PowerShell:
Set-OwaMailboxPolicy documentation.
Compliance considerations:
No compliance considerations identified, review as appropriate for your organization.