How to open winmail.dat

Updated February 21, 2017

When Microsoft Outlook is not properly configured, attachments may sometimes be sent in the format of winmail.dat. This is a binary file format that can only be read by Microsoft Outlook and is basically useless to other applications. With a simple and free online service such as, users can upload their .dat files, have the information and attachments extracted, download the resulting files, and open and view them.

Open a Web browser and navigate to

Click the "Browse" button and select the winmail.dat file.

Click the "Send file" button to upload the file.

Click on the "Results" tab to download the contents of the winmail.dat file.


The maximum size of your winmail.dat file cannot exceed 5 MB.

Things You'll Need

  • Internet access
  • Winmail.dat


Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Diana Braun began her writing career as a consultant and technical writer for a software company focusing on how-to, training, white paper, and internal process documentation. After two years, Braun left to pursue her entrepreneurial dreams. Since then, she has launched several startups including a t-shirt business, an online marketing and advertising t-shirt distribution business, and an entertainment site. She currently resides in South Florida.