Open DAT File

Information, tips and instructions

Winmail.dat File Handling

Microsoft Outlook uses Transport Neutral Encapsulation Format (TNEF) as a transmission format for e-mail messages. TNEF allows transferring richly encoded messages with attachments, color, embedded OLE documents, forms, voting buttons and meeting requests. This format is fully supported by all Microsoft Outlook versions but has limited support on other mail clients which prefer Multipurpose Internet Mail Extensions (MIME) e-mail format.

If you don’t have Microsoft Outlook installed, you can still read winmail.dat file using 3rd party tools. Below we list a free TNEF opener tool for each operating system.

For Mac OS you can download free tnefDD tool. TnefDD is a program for Mac OS X which can extract attachments from TNEF formatted files.

  • Decode files in TNEF format (winmail.dat)
  • Parse and save attachment dates to keep track of file versions
  • Directly open attachments from TNEF file without copying them to a local disk

For Windows 10 and later you can use Winmail.dat Reader and Saver app. It has following features:

  • Open, convert and save the files from winmail.dat email attachments sent by Microsoft Outlook and Exchange
  • Easy-to-use graphic interface (no command-line tool)
  • Displays the original message subject and body

If you use Windows 7 or earlier you can download Winmail Opener from Eolsoft. It supports:

  • RTF message text extraction
  • Drag-and-drop of TNEF files to Winmail Opener
  • Drag-and-drop decoded attachments from Winmail Opener to any other locations
  • Command line parameters support for batch processing
  • Support of multiple languages (21 language supported)

If you don't want to download a standalone application you can use an online service for winmail.dat file conversion provided by website.

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File Extension Info
Data file
Dependes on type of data
DAT File Opens With
Microsoft Outlook
Windows Registry REG tool

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