How to Fix Excel Attachment Arriving as a DAT File in Email
Question details
The user needs to prevent Excel workbooks sent via email from arriving as unreadable .dat files so recipients can open the spreadsheets normally.
- Product
- Microsoft Excel and Outlook
- Device & OS
- not provided
- Scenario
- Sending an Excel workbook from a computer via email (typically Outlook) to a recipient using a webmail service.
- Observed behavior
- The Excel attachment is automatically converted into a .dat file during transit, preventing the recipient from opening the spreadsheet.
Verify whether the recipient is using a web-based email service (like Gmail or Yahoo) or a desktop client like Microsoft Outlook, as this issue primarily occurs when sending from Outlook desktop to webmail clients.
Adjust Email Sending Methods
Bypass the email client's format conversion by sending the file from a different account or directly to another Outlook address.
This issue, commonly known as the 'winmail.dat' error, frequently happens when Microsoft Outlook sends rich text emails to web-based email clients that cannot decode them.
Ask the recipient if they have an alternative Microsoft Exchange or Outlook email address. Forward the email containing the Excel attachment to that specific address.
Instead of using the Microsoft Outlook desktop application, log into your email provider's web interface (e.g., your browser) and attach the Excel workbook there.
If the file arrives correctly but fails to preview, instruct the recipient to save the attachment to their local hard drive first before double-clicking to open it.
Change Outlook Default Message Format to HTML
Prevent Outlook from sending files in Rich Text Format (RTF), which is the root cause of attachments turning into .dat files.
Switch to WPS Office for Hassle-Free Spreadsheet Sharing
If you frequently encounter formatting errors, attachment bugs, or compatibility issues with Microsoft Office, consider switching to WPS Office. It provides a lightweight, highly compatible, and free alternative with familiar interfaces, allowing you to easily create, save, and share your spreadsheets seamlessly.
- 1. Download and Install: Download WPS Office Free from the official website and run the quick installation process.
- 2. Open Your Workbooks: Launch WPS Spreadsheet and open any of your existing Excel (.xlsx or .xls) files without losing formatting.
- 3. Share via Link: Use the built-in 'Share' feature to generate a direct link to your spreadsheet, completely avoiding the .dat email attachment issue.
Frequently Asked Questions
Why do my Excel attachments turn into DAT files?
This happens when emails are sent from Microsoft Outlook using the Rich Text Format (RTF). Many webmail services and non-Outlook email clients cannot decode RTF, so they bundle the formatting data and the original attachment into an unreadable file typically named 'winmail.dat'.
Can the recipient extract the Excel file from the DAT file?
Yes, the recipient can use free online winmail.dat extractors or third-party extraction tools to decode the file and retrieve the original Excel workbook. However, preventing the issue by changing the sender's email format is the most reliable long-term solution.
Does saving the file as a PDF prevent it from becoming a DAT file?
Not necessarily. If your email client is configured to send messages in Rich Text Format, any attachment—whether it is a PDF, Word document, or Excel spreadsheet—can get bundled into a .dat file for webmail recipients. You must change the email format to HTML.
How can I share an Excel file without sending an email attachment?
You can upload your Excel workbook to a secure cloud storage service (like WPS Cloud, Google Drive, or OneDrive) and share a direct link with your recipient. This guarantees they will be able to access or download the file without email formatting conflicts.
