Teams turns on file sharing in chats with outsiders by default
Reviewed by Helen Jones
Microsoft will change the default for file sharing in external, federated Teams chats from Disabled to Enabled. Message Center notice MC1479514, published 25 September 2026, says rollout starts in late October 2026 and should finish by late November 2026 for Targeted Release and General Availability, including GCC, GCC High, and DoD. The flip applies even if an organisation had already set the capability to Disabled. Users in external one-to-one, group, and meeting chats will get an Attach file option instead of being limited to pasting existing links. Files land in the sender's OneDrive and still follow existing OneDrive, SharePoint, and security controls. There is no Teams admin center switch in the notice. Admins who want the old behaviour must use PowerShell: Set-CsTeamsFilesPolicy with FileSharingInChatsWithExternalUsers. Microsoft Learn still describes the setting as off by default.
Until now, attaching files in chats with people outside the tenant was an explicit opt-in. Many small admin teams treated that as a quiet control: guests and federation could talk, but the paperclip stayed off unless someone chose to turn it on. Pasting a link still worked, so the lockdown was easy to miss in day-to-day support. After the tenant receives this update, that prior Disabled choice does not stick. The paperclip comes back unless you reapply the policy. Because the control is PowerShell-only and can take hours to show in clients, a governance decision you thought was settled can reverse without a banner in the Teams admin center.
Analysis
This is a trap to avoid if you already blocked attach-file in external chats, not a feature to rush into testing. After the rollout hits your tenant, reapply FileSharingInChatsWithExternalUsers as Disabled with Set-CsTeamsFilesPolicy and confirm the paperclip is gone in an external test chat.
Source note
Pulse published by Collab365 Spaces, reviewed by Helen Jones on . Cite as "Teams turns on file sharing in chats with outsiders by default", Collab365 Spaces. 3 sources referenced.