6.5 Ensure additional storage providers are restricted in Outlook on the web

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This setting allows users to open certain external files while working in Outlook on the web. If allowed, keep in mind that Microsoft doesn't control the use terms or privacy policies of those third-party services.

Ensure AdditionalStorageProvidersAvailable are restricted.


By default additional storage providers are allowed in Office on the Web (such as Box, Dropbox, Facebook, Google Drive, OneDrive Personal, etc.). This could lead to information leakage and additional risk of infection from organizational non-trusted storage providers. Restricting this will inherently reduce risk as it will narrow opportunities for infection and data leakage.


Impact associated with this change is highly dependent upon current practices in the tenant. If users do not use other storage providers, then minimal impact is likely. However, if users do regularly utilize providers outside of the tenant this will affect their ability to continue to do so.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.


Restrict additional storage providers are restricted using PowerShell:

Connect to Exchange Online using Connect-ExchangeOnline.

Run the following PowerShell command:

Set-OwaMailboxPolicy -Identity OwaMailboxPolicy-Default -AdditionalStorageProvidersAvailable $false

Run the following Powershell command to verify that the value is now False:

Get-OwaMailboxPolicy | Format-Table Name, AdditionalStorageProvidersAvailable

Default Value:

Additional Storage Providers - True

See Also