3 Best Ways to Open Winmail Dat File Online Free 2022

Bianca Huang
August 18, 2022 Preview 10.9K Preview 0
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When we talk about opening dat files, we refer to Winmail.dat files, it is a file format containing email subject, email receiver and sender, message body and the attachment, with its original formatting in Microsoft Outlook. A dat file is created when the email recipient is not using Microsoft Outlook email client to read emails, in this case, a winmail.dat file opener is required.

It seems that there are so many users looking for solutions to open Winmail dat files online free, without installing any 3rd party Winmail viewers. For this reason, here we list 3 best online free Winmail.dat file opener, so you can open and view Winmail.dat files on Mac, on Windows PC, even on mobile device.

#1 Winmaildat.com

Winmaildat.com ranks as No.1 in the Google search result for “open dat file online” and it does deserve such a good ranking.

It is an online free file viewer to open winmail.dat or ATT0001 files, as it claims, it is easy to use and there is no hidden costs, registration or email submission required, but there is a max file size: 50MB. While, I don't think such a file size limit will cause any troubles to most of our users, since we won’t attach too many too large attachment in an email.


  1. 100% free
  2. Easy to use
  3. Upload Dat file from local folder or via URL
  4. Allow downloading email body in RTF format
  5. Save email attachment to your computer


  1. Cannot preview the message body
  2. Processing takes time
  3. Show duplicate attachments
  4. Max file size: 50MB

How to Open Dat File Online Free with Winmaildat.com?

  1. Go to Winmaildat.com.
  2. Click Choose File to upload your file or directly enter the URL for the Winmail.dat file.winmaildat01
  3. Click Start to process.
  4. Download the message body and attachments.winmaildat02


#2 Winmail-dat.com

Winmail-dat.com is another online free dat file opener, it allows users to read the message body directly on its website. However, it has more limitations. For example, you can only upload Winmail.dat file not exceeding 5MB, you won’t be able to download some attachments…


  1. 100% free
  2. Easy to use
  3. View message body on the webpage
  4. Allow downloading attachments


  1. Decoding takes time
  2. Max file size: 5MB
  3. Cannot read attachments sometimes (e.g empty picture)

How to Open Dat File Online Free with Winmail-dat.com?

  1. Go to Winmail-dat.
  2. Click Choose File to upload your Winmail.dat file.winmail-dat01
  3. Click Decode to open the Winmail file online.
  4. Then read the message body and download the attachments to your computer.winmail-dat02


#3 Winmaildat.de

It is an online free Winmaildat opener in Germany, bearing a lot of resemblances with Winmaildat.com. It allows users to read and view Winmail.at or ATT0001, with a max file size limit of 100 MB. However, it may list duplicate files after decoding, like duplicate message body in RTF files, or duplicate attachments. Even, there are sometimes you cannot open the attachment after downloading.


  1. 100% free to use
  2. Easy to use
  3. Save message body in RTF format
  4. Download attachments or all files in a zip
  5. Sufficient max file size limit: 100 MB


  1. Cannot view message body on the website
  2. Processing takes time
  3. Show duplicate attachments
  4. Cannot open the downloaded attachments sometimes

How to Open Dat File Online Free with Winmaildat.de?

  1. Go to Winmaildat.de.
  2. Click Choose Files to upload your Winmail.dat file.winmaildat-de01
  3. Click Upload.
  4. Download all winmail.dat message or attachments to your computer.winmaildat-de02

Comparison of Best 3 Online Free Winmail.dat Viewers

  Winmaildat.com Winmail-dat.com Winmaildat.de
Overall Rating 4.0/5.0 3.8/5.0 3.8/5.0
Allow Preview Message Body No Yes No
Allow Download Attachments Yes Yes Yes
Process Speed Medium Slow Slow
File Size Limit 50MB 5MB 100MB


Is There Any Tool to Open Winmail Dat File Online by Converting Dat to PDF?

As you can see, there aren’t too many choices on online free Winmail.dat file viewer. In the first beginning, I was planning to dig some Winmail.dat to PDF online free tools to you, because there are so many tools offered online to export various files as PDF and it is much easier to read a PDF file than to read a Winmail.dat file. However, I later realized that there was no online free tool to save Winmail.dat as PDF format.

Maybe this is for the reason that a Winmail.dat may include attachments, when converting Winmail.dat to PDF, you have no way to export all those attachments to the PDF. It is pitiful, but we already have 3 best online free Winmail.dat viewers as we listed above.


Best Way to Open Winmail.dat File 2022 (Mac & Windows)

Being free, online Winmail.dat viewers are indeed popular, but not all our users finally pick them as the tool to open their Winmail.dat files, due to their disadvantages. To extract all the information and attachments from a Winmail.dat file accurately, we may still need a processional Winmail.dat viewer.

Best Winmail.dat Viewer for Mac 2022

Cisdem Document Reader is definitely the winner in this filed, which has won countless positive feedbacks from users and authorities. 

It is a mac program to view and convert multiple Windows-based files, including Winmail.dat, Visio, DjVu, WordPerfect, WPS, XPS, OXPS and PDF. With its viewing tools, you can read any Winmail.dat files comfortably. Additionally, you will be allowed to convert files to PDF format.

Main Features of Cisdem Document Reader

  • Open and view 8 file formats, including Winmail.dat
  • View multiple files the same time
  • Allow zoom, turn pages, rotate, bookmark, print, extract images, search
  • Convert files to PDF, Text or Image format
  • Load files fast for reading

How to Open Winmail.dat Files with Cisdem?

  1. Download and install Cisdem Document Reader for Mac.
    Free Download
  2. Drag and drop Winmail.dat files to the program.cisdem winmail.dat file opener01
  3. View Winmail.dat files, also you can save the Winmail.dat attachments as individual file to your Mac.cisdem winmail.dat opener02

Best Winmail.dat Viewer for Windows 2022

It is much easier to open Winmail.dat files on Windows and there are more choices for such a Winmail.dat viewer. Winmail.dat Reader and Saver is the best.

It works on Windows 10, allowing users to open, convert and save files from Winmail.dat, it is extremely easy to use.

Main Features of Winmail.dat Reader and Saver

  • Read Winmail.dat or ATT0001.dat files
  • Convert Winmail.dat files
  • Save attachments from Winmail.dat file
  • Display the original message subject and body

How to Open Winmail.dat Files with Winmail.dat Reader and Saver?

  1. Download and install Winmail.dat Reader and Saver to your Windows PC.
  2. Then locate your Winmail.dat files and open in this Windows program.winmail dat viewer for windows
  3. Check the displayed message body and save the attachments to your Windows PC according to your needs.


It is not easy to open and view Winmail.dat files, but there are online free tools offered to help on this, and they do work. When opening Winmail.dat files online free, users are highly recommended not to upload confidential emails due to potential risk of information leakage. If you need to work on Winmail.dat files very often, just download and install a professional opener to do the job.

Bianca Huang
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Bianca is a senior tech editor and strategist at Cisdem with Over 10 years of experience on PDF related solutions which covers all document editing, annotating, converting and managing etc.

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