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Fix Outlook PDF Attachment Opening as DAT File on iPhone
Question details
The user is unable to open a PDF attachment sent via Outlook on their iPhone because it converts into an unreadable DAT file, and the third-party PDF reader app freezes on the welcome screen.
- Product
- Microsoft Outlook and Adobe Acrobat for iOS
- Device & OS
- iPhone 11, iOS 14.3
- Scenario
- Attempting to view a PDF attachment received via an Outlook email on an iPhone.
- Observed behavior
- The PDF file is received as an unreadable DAT file (winmail.dat), and attempting to use the default PDF reader app causes it to freeze.
Verify with the sender if they are using Microsoft Outlook to send the email, as this issue is typically caused by Outlook's Rich Text Format (RTF) packaging attachments into a winmail.dat file.
Request the Sender to Change Outlook Email Format to HTML
The most permanent fix is for the sender to adjust their Outlook message format, preventing PDFs from being packaged as unreadable DAT files.
When emails are sent from Outlook using Rich Text Format, standard attachments like PDFs are often bundled into a winmail.dat file that Apple Mail cannot natively read. Asking the sender to switch to HTML format resolves this at the source.
Ask the sender to open Microsoft Outlook on their PC, click on 'File' in the top left corner, and select 'Options'.
In the Outlook Options window, select 'Mail' from the left sidebar. Under the 'Compose messages' section, change the 'Compose messages in this format' dropdown to 'HTML'.
Scroll down to the 'Message format' section and ensure that 'When sending messages in Rich Text format to Internet recipients' is set to 'Convert to HTML format'.
Click 'OK' to save the settings, and ask the sender to attach the PDF to a new email and resend it to your iPhone.
Extract the PDF Using a Third-Party Viewer App
If you cannot contact the sender to change their settings, you can use an iOS app designed to extract files from winmail.dat attachments.
Resolve the PDF Reader App Freezing Issue
Fix the issue where your third-party PDF reader app freezes at the welcome screen by forcing it to restart or reinstalling it.
View and Manage PDF Attachments Easily with WPS Office
Avoid app freezes and seamlessly open, view, and annotate PDF attachments on your iPhone using WPS Office. It provides a stable, highly compatible alternative to heavy PDF readers.
- 1. Install the App: Download and install WPS Office for free from the Apple App Store on your iPhone.
- 2. Open the Email Attachment: Once the sender sends a standard PDF, open the email and tap on the attachment.
- 3. Share to WPS Office: Tap the 'Share' icon and select 'Open in WPS Office' from the list of available apps.
- 4. Read and Edit Smoothly: Enjoy a stable reading experience and utilize built-in tools to annotate or edit the PDF as needed.
Frequently Asked Questions
Why do PDF attachments turn into DAT files on my iPhone?
This occurs when an email is sent from Microsoft Outlook using the Rich Text Format (RTF). Apple's Mail app on iOS cannot interpret this proprietary formatting, causing the email and its attachments to be bundled into an unreadable winmail.dat file.
Can I prevent my Outlook from sending DAT files to iPhone users?
Yes. In Outlook on your PC, go to File > Options > Mail. Under the 'Message format' section, ensure that 'When sending messages in Rich Text format to Internet recipients' is set to 'Convert to HTML format'.
Is there a way to extract a PDF from a winmail.dat file without third-party apps?
On an iPhone, it is difficult without a dedicated app. However, you can forward the email to a web-based email service like Gmail or Outlook.com. These webmail clients can automatically decode the winmail.dat file and display the PDF attachment natively in your browser.
How do I stop my PDF app from freezing on iOS 14?
App freezing is often caused by software glitches or outdated app versions. Try force-closing the app from the App Switcher. If the problem persists, ensure your iOS is updated to the latest version and try deleting and reinstalling the PDF reader app.
