How to Open a Winmail.dat File

Occasionally, when receiving emails, you might encounter a winmail.dat file as an attachment, especially if the sender uses Microsoft Outlook. This file contains formatted data, such as text styles and embedded files, but often appears as an unknown file in non-Outlook mail clients. This guide explains what winmail.dat is and how you can open it.

What is Winmail.dat?

The winmail.dat file is generated by Microsoft Outlook and other Microsoft Office products. It is used to transmit text formatting (like bold or italics) and other elements compatible only with the Outlook mail client. Unfortunately, many other email clients, like Gmail or Apple Mail, cannot interpret this file, so they display it simply as winmail.dat.

Why Does the Winmail.dat File Appear?

This issue occurs when the sender emails in Rich Text Format (RTF), which may not be compatible with all email clients. Outlook converts these messages into winmail.dat to deliver RTF formatting, which can cause difficulties for recipients using different email systems.

Ways to Open a Winmail.dat File

1. Using Online Services

The simplest way to open a winmail.dat file is by using an online service that automatically converts the file into a readable format. Some popular services include:

  • Winmaildat.com — upload the file to retrieve its contents in a readable format like PDF.

2. Using Specialized Software

If you prefer to open the file directly on your computer, you can install specialized software. Some popular options include:

  • Winmail Opener (Windows) — a free app for reading and converting winmail.dat files into readable formats.
  • Letter Opener (macOS) — an app for Mac users that opens and extracts the contents of the file.
  • TNEF’s Enough — a free app for Mac that allows you to extract attachments from winmail.dat.

3. Requesting Format Change from the Sender

If you frequently receive winmail.dat files from the same sender, you could ask them to change the email format from RTF to HTML or plain text. This can help prevent the creation of winmail.dat files in the future. To do this, the sender should:

  1. Open Microsoft Outlook.
  2. Go to Mail Settings > Message Formatting.
  3. Select either HTML or Plain Text instead of RTF.