MC1253750 - Microsoft 365 Copilot: Upload local files now supports .eml and .msg file types

Introduction

We’re adding support for .eml and .msg file uploads in Microsoft 365 Copilot, including Copilot Chat and the Microsoft 365 Copilot app. This update makes it easier for users to include email files as context when prompting Copilot, helping them generate more relevant and grounded responses.

This message is associated with Microsoft 365 Roadmap ID 552591.

When this will happen

• General availability (Worldwide): Rollout begin in late February 2026 and is expected to complete by late March 2026.

How this affects your organization

Who is affected

• All users in Microsoft 365 tenants who have access to Microsoft 365 Copilot Chat or the Microsoft 365 Copilot app.

What will happen

• Users will be able to upload .eml and .msg files directly when interacting with Copilot.
• Uploaded files can be used as grounding context for prompts.
• This feature is available by default; no admin configuration is required.
• There is no change to existing policies governing file handling or data access.

What you can do to prepare

No action is required. This feature will roll out automatically.

Optionally, you may:

• Inform helpdesk or support staff in case users ask about new upload capabilities.
• Update internal Copilot usage or prompt‑writing guidance to reflect expanded supported file types.

Compliance considerations

No compliance considerations identified. Review as appropriate for your organization.