How to open winmail.dat files on Ubuntu and Debian Linux

Winmail.dat files are a unique file format utilized primarily by Microsoft Outlook. These files serve as containers for attachments sent through emails formatted in rich-text. This format can cause compatibility issues, particularly when users of non-Microsoft email clients, such as those on Linux systems, receive attachments.

What is a Winmail.dat File?

When an Outlook user sends an email using the rich-text format, it often encapsulates attachments in a winmail.dat file. This special format preserves the formatting, fonts, and colors as intended by the sender. However, this can lead to difficulties for recipients not using Outlook, as they may receive the winmail.dat file instead of the actual attachment.

How to Open Winmail.dat Files on Linux

Linux users can access the contents of winmail.dat files by using a utility called tnef, which stands for Transport Neutral Encapsulation Format. This utility extracts the contents of the winmail.dat file, making it possible to access the attachments.

Installation of TNEF

To install the tnef utility on a Debian or Ubuntu Linux system, open the terminal and enter the following command:

sudo apt install tnef

This command will download and install tnef from the Linux repository.

Using TNEF to Extract Files

Once installed, you can extract files from a winmail.dat file by following these steps:

  1. Open a terminal window.
  2. Navigate to the directory where the winmail.dat file is saved.
  3. Execute the command:
    tnef winmail.dat

This will extract all files stored in the winmail.dat file into the current directory.


Extracting winmail.dat to a Specific Directory

To extract files to a specific directory, use:

tnef winmail.dat --directory=/path/to/directory

Viewing Contents Without Extracting

To view the contents of a winmail.dat file without extracting them, use:

tnef --list winmail.dat

Frequently Asked Questions

Can winmail.dat files contain viruses?

Like any email attachment, winmail.dat files can contain harmful content. Always ensure your system has up-to-date antivirus software.

Why do I keep receiving winmail.dat files instead of regular attachments?

This happens because the sender is using Outlook's rich-text format. Ask the sender to resend the attachment using plain text or HTML format.

Can I open winmail.dat files on other operating systems?

There are utilities and programs available for Windows and macOS as well, such as Winmail Opener for Windows and Letter Opener for macOS.

Is there a way to prevent Outlook from sending winmail.dat files?

Outlook users can change their settings to send emails in HTML or plain text format to avoid creating winmail.dat files.