Microsoft 365 Copilot Cannot Summarize Email With Attachment: Fix

You open an email in Outlook with an attached PDF or Word file, click the Copilot summarize button, and Copilot returns an error or a generic summary that ignores the attachment. This happens because Copilot for Microsoft 365 can read the email body but cannot always access the content of attached files unless the attachment is stored in a supported format and location. This article explains why Copilot fails to summarize attachments and provides the exact steps to fix the issue so you can get a complete summary that includes attachment data.

Why Copilot Cannot Summarize Attachments in Outlook

Copilot for Microsoft 365 processes email summaries by reading the email body and any data that is accessible through Microsoft Graph. When you attach a file directly from your computer, the file is sent as a binary copy that resides only in the email message. Microsoft Graph cannot read the content of a file that is embedded as a raw attachment because the file has no metadata or storage path that Copilot can query. Copilot is designed to work with files stored in Microsoft 365 cloud services like OneDrive for Business or SharePoint Online. If the attachment is a local file, Copilot sees only the file name and extension, not the content. This is a deliberate security and design limitation: Copilot cannot pull data from files that are not stored in a location where permissions and indexing are managed by Microsoft 365.

Supported File Formats for Attachment Summarization

Even when the attachment is stored in OneDrive, Copilot can only summarize certain file types. The supported formats are:

• Word documents (.docx)
• Excel workbooks (.xlsx)
• PowerPoint presentations (.pptx)
• PDF files (.pdf)
• Text files (.txt)

Files in unsupported formats such as .zip, .jpg, .mp3, or .exe are ignored by the summarization process. Copilot will summarize only the email body if the attachment is not a supported type.

Permission and Licensing Requirements

To use Copilot summarization with attachments, you need an active Copilot for Microsoft 365 license. The license must be assigned to your user account in the Microsoft 365 admin center. Additionally, the file in OneDrive or SharePoint must have sharing permissions that allow Copilot to read it. If the file is shared with you but you do not have at least read access, Copilot cannot read its content.

Steps to Fix Copilot Attachment Summarization

Follow these steps to resolve the issue. The primary fix is to store the attachment in OneDrive before sending or before asking Copilot to summarize it.

1. Remove the local attachment from the email
   Open the email in Outlook. Right-click the attachment and select Remove Attachment. Do this for each file that was attached from your local drive.
2. Upload the file to OneDrive for Business
   Go to onedrive.com and sign in with your work or school account. Click Upload and select the file from your computer. Wait for the upload to complete. The file must be in a supported format: .docx, .xlsx, .pptx, .pdf, or .txt.
3. Attach the file from OneDrive in Outlook
   In the email, click Attach File. Instead of choosing Browse This Computer, select Browse Cloud Locations. Navigate to the file in OneDrive or SharePoint and select it. The file now appears as a cloud attachment with a small cloud icon.
4. Send a new email or forward the original
   If the email has already been sent, you cannot modify it. Instead, forward the email to yourself. Before sending, remove the old local attachment and attach the OneDrive version as described in step 3. Send the email.
5. Use Copilot to summarize the new email
   Open the email with the cloud attachment. Click the Copilot icon in the ribbon or select Summarize from the Copilot pane. Copilot now reads the email body and the attachment content and returns a combined summary.

Alternative Method: Use Copilot in Word or Excel Directly

If you do not need the summary inside Outlook, you can open the attachment directly in its native app and use Copilot there. For example, open a Word document from OneDrive, click the Copilot icon in Word, and ask it to summarize the document. This bypasses the Outlook attachment limitation entirely.

If Copilot Still Cannot Summarize the Attachment

After attaching the file from OneDrive, Copilot may still fail to include the attachment content. Here are the most common remaining issues and their fixes.

Copilot Returns Summary of Email Body Only

If Copilot ignores the attachment even when it is stored in OneDrive, the file may be in an unsupported format. Check the file extension. Rename the file to a supported format if possible. For example, save a .rtf file as .docx. If the file is a scanned PDF with no selectable text, Copilot cannot read it because it requires text-based content. Use OCR software to convert the PDF to searchable text first.

Copilot Shows an Error About Permissions

An error message like Copilot cannot access the file or Something went wrong indicates a permission issue. Right-click the file in OneDrive and select Share. Ensure the recipient or your own account has at least Can View permission. If the file is in a SharePoint document library, check that the library allows external sharing if needed. Also confirm that your Copilot license is active. Go to Microsoft 365 admin center, select Users, find your account, and verify that Copilot for Microsoft 365 is listed under Licenses and apps.

Copilot Does Not Appear in Outlook at All

If the Copilot button is missing from the Outlook ribbon, the add-in may be disabled or not installed. Go to Outlook > Get Add-ins > Admin Managed. Look for Microsoft Copilot. If it is listed but disabled, click the three dots next to it and select Enable. If it is not listed, contact your IT administrator to assign the Copilot license and deploy the add-in through the Microsoft 365 admin center.

Item	Local Attachment	OneDrive or SharePoint Attachment
File location	Embedded in the email message	Stored in cloud storage
Copilot can read content	No	Yes, if format is supported
Requires cloud upload	No	Yes
Supported formats	Any format but not readable	.docx, .xlsx, .pptx, .pdf, .txt
Permission check needed	No	Yes, read access required

You can now fix Copilot attachment summarization by confirming the file is stored in OneDrive or SharePoint and that it uses a supported format. After re-attaching the file as a cloud attachment, Copilot reads both the email body and the attachment content to provide a complete summary. For files that cannot be moved to the cloud, use Copilot directly in the native app such as Word or Excel to summarize the document separately.