Why Teams Blocks File Attachments in External Chats (and the PowerShell Fix)
TL;DR
- By default, Microsoft Teams prevents users from attaching files in chats that include external participants; the attach option disappears and drag-and-drop is blocked.
- The behavior is controlled by the FileSharingInChatsWithExternalUsers setting in the Teams Files Policy, which ships Disabled.
- As of May 2026 the setting is not exposed in the Teams Admin Center and can only be changed through the MicrosoftTeams PowerShell module.
- Modifying the Global policy applies to the entire tenant; scope a custom policy instead if only some users need external file sharing.
- Whether external recipients can actually open the files still depends on SharePoint external sharing settings, which are managed separately.
There is a Teams setting almost nobody knows exists, and it generates real tickets: users chatting with a client, vendor, or partner outside the organization discover the attach option is simply gone. The plus icon offers no file attachment. Dragging a file from File Explorer into the chat gets a red X.
That is not a glitch. It is a default policy, and most IT admins and end users have no idea it is there. The fix takes four PowerShell commands, and we will walk through all of them.
What is actually blocking the attachment?
Microsoft Teams controls file-sharing behavior through a Files Policy. One specific setting inside that policy, FileSharingInChatsWithExternalUsers, determines whether users can attach files when chatting with someone outside your organization.
By default, that setting is Disabled.
The result: users in an external chat lose the native file attachment experience entirely. They can still paste a SharePoint or OneDrive link into the chat manually, but clicking the plus icon to attach a file directly is gone, and drag-and-drop is blocked.
For teams that collaborate regularly with clients, vendors, or partners, this becomes a daily friction point. People start emailing files, using personal cloud storage, or inventing workarounds, and none of those are wins from a security or workflow perspective.
How do you turn it on?
As of May 2026, this setting is not configurable through the Teams Admin Center UI. It requires PowerShell.
# Step 1: Install the module
Install-Module -Name MicrosoftTeams -Force -AllowClobber
# Step 2: Import and connect
Import-Module MicrosoftTeams
Connect-MicrosoftTeams
# Step 3: Check current policy
Get-CsTeamsFilesPolicy
# Step 4: Enable external file sharing
Set-CsTeamsFilesPolicy -Identity "Global" -FileSharingInChatsWithExternalUsers Enabled
Read this before you run it
- Global means everyone. Modifying the Global policy applies the change across your entire tenant. If only specific users or groups should have this capability, create a custom policy and assign it to them instead of touching Global.
- Propagation takes time. In larger environments, changes can take an hour or more to propagate through Teams. In practice, waiting up to 24 hours before concluding something went wrong is a safe approach. Run the Get-CsTeamsFilesPolicy check first to confirm the command ran; if the value shows Enabled, the change is in flight.
- SharePoint and OneDrive settings are separate. This policy controls the file attachment experience inside Teams chat. Whether external users can actually access those files depends on your SharePoint external sharing settings, managed independently in the SharePoint Admin Center.
- Always verify after. A quick Get-CsTeamsFilesPolicy after setting the policy confirms the command executed successfully and gives you a record of the current state.
Frequently asked questions
How long does the policy change take to apply?
Changes can take an hour or more to propagate in larger environments, and waiting up to 24 hours before concluding something went wrong is a safe approach. If Get-CsTeamsFilesPolicy shows the value as Enabled, the change is in flight.
Does enabling this also let external users open the files?
Not by itself. This policy controls the attachment experience inside Teams chat. Actual file access for external users depends on your SharePoint external sharing settings, managed independently in the SharePoint Admin Center.
Can you enable it for only certain users?
Yes. Create a custom Teams Files Policy with FileSharingInChatsWithExternalUsers enabled and assign it to the specific users or groups, leaving the Global policy untouched.
How many defaults like this are hiding in your tenants?
One undocumented toggle caused this friction. CloudCapsule reads 250+ settings like it across every tenant you manage in about 60 seconds, so the surprises show up in a report instead of a ticket.
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Written by
Nick Ross
CEO · Microsoft MVP · Founder, T-Minus 365
Nick is not just a CEO, he's a respected thought leader and influencer in the MSP space. Tens of thousands of MSPs learn through his YouTube channel, T-Minus365. Nick has been honored as a three-time Microsoft MVP for his educational content; his expertise and influence are the backbone of our mission, ensuring that you are in the best hands when it comes to security.
Nick joined Pax8 in 2017, where he would ultimately oversee product management for PSA and Microsoft integrations. Following his tenure at Pax8, Nick has continued to demonstrate his leadership prowess as an executive at various MSPs, culminating in his most recent role at Sourcepass.
Nick holds a Bachelor's Degree in Business Management from Florida State University, as well as a Minor Degree in Entrepreneurship. In his free time, Nick is an avid hiker, reader, and fitness-junkie.
