Copilot in Outlook Cannot Process .msg Attachments: Workaround

You are working in Outlook and ask Copilot to summarize or analyze a .msg file attached to an email. Instead of generating a response, Copilot returns an error or does nothing. This limitation is by design. Copilot can process .pdf, .docx, .xlsx, and .txt files but cannot read the proprietary .msg email format. This article explains why Copilot cannot handle .msg attachments and provides a step-by-step workaround that lets you extract the content you need.

Why Copilot Cannot Read .msg Attachments

The .msg format is a proprietary file structure used by Microsoft Outlook to store individual email messages. This format includes the email header, body, attachments, and metadata in a single binary file. Copilot, as of the current release, only supports text-based and common document formats for processing. The supported list includes .pdf, .docx, .xlsx, .pptx, and .txt. The .msg format is not on that list because its internal structure requires Outlook itself to parse the content.

When Copilot encounters an unsupported file type, it cannot extract the text or metadata needed to answer your prompt. The system returns a message such as “I cannot process this attachment” or simply ignores the file. This is not a bug. It is a deliberate limitation based on the file formats Copilot is designed to analyze.

The workaround requires you to convert the .msg file into a format Copilot can read. You can do this manually for a single file or use automation for multiple files.

Steps to Convert a .msg Attachment for Copilot

1. Save the .msg attachment to your computer
   Open the email that contains the .msg attachment. Right-click the attachment and select Save As. Choose a folder on your local drive and click Save.
2. Open the .msg file in Outlook
   Double-click the saved .msg file. It opens as a new email in Outlook. You can also drag the file into an open Outlook window.
3. Copy the email body text
   Select all text in the email body by pressing Ctrl+A. Copy it with Ctrl+C. If the email contains images or tables, only the text is copied.
4. Paste the text into a new email or Copilot chat
   Open a new email in Outlook or open the Copilot pane. Paste the text with Ctrl+V. You can now ask Copilot to summarize, analyze, or extract information from the pasted content.
5. Alternative: Save as .txt or .pdf
   After opening the .msg file, go to File > Save As. In the Save as type dropdown, select Plain Text (.txt) or PDF (.pdf). Save the file. Attach this new file to an email or upload it to a Copilot-supported location such as OneDrive. Then ask Copilot to process it.

Using Power Automate for Bulk Conversion

If you need to process many .msg files, create a Power Automate flow. Use the Outlook connector to trigger when a new email with a .msg attachment arrives. Add a step to save the attachment to OneDrive. Then use the Convert file action to change .msg to .txt or .pdf. Finally, upload the converted file to a SharePoint document library where Copilot can access it.

1. Create a new automated cloud flow
   Go to Power Automate and select Create > Automated cloud flow. Choose the trigger When a new email arrives (Outlook).
2. Add a condition to filter .msg attachments
   Add a Condition action that checks if the attachment name ends with .msg. This prevents the flow from running on every email.
3. Save the attachment to OneDrive
   Add a Create file action for OneDrive for Business. Use the attachment content and name from the trigger.
4. Convert the file
   Add a Convert file action. Set source to .msg and target to .txt or .pdf. This action requires a premium Power Automate license.
5. Store the converted file
   Add a Create file action to save the converted content to a SharePoint document library that has Copilot indexing enabled.

If Copilot Still Cannot Process the Converted File

Copilot says the file is too large

Copilot has a file size limit of approximately 3 MB for processing. If the converted .txt or .pdf file exceeds this limit, split the content into smaller segments. Create separate files for each logical section of the original email. Then ask Copilot to process each file individually.

Copilot ignores the pasted text

When you paste text directly into the Copilot chat pane, Copilot may treat the conversation as a new session and lose context. To avoid this, paste the text into a new email in Outlook and then open the Copilot pane within that email. Copilot will treat the email body as the current context and respond to prompts about it.

Copilot returns generic answers about the email format

If you attach a .msg file and Copilot responds with information about the file format instead of the content, it means Copilot cannot read the file. Remove the .msg attachment and use one of the conversion methods described above. Do not ask Copilot to “read” or “open” the .msg file. Instead, provide the text directly.

Copilot Supported Formats vs .msg: Comparison

Item	Supported Formats	.msg Format
File types	.txt, .pdf, .docx, .xlsx, .pptx	.msg
Text extraction	Automatic by Copilot	Requires manual conversion
Metadata access	Full (subject, author, date)	Not available to Copilot
Bulk processing	Supported via SharePoint or OneDrive	Requires Power Automate or manual steps
Security	Standard Microsoft 365 compliance	Same as any Outlook attachment

The table above shows that Copilot can automatically extract text from common document formats. The .msg format requires manual or automated conversion before Copilot can process the content.

You can now convert any .msg attachment into a Copilot-friendly format by copying the body text or saving as .txt or .pdf. For recurring tasks, set up a Power Automate flow to handle the conversion. Try pasting the email body into a new Outlook message and asking Copilot to summarize the key points. This approach bypasses the .msg limitation entirely and gives you the same Copilot capabilities you expect from supported file types.