Winmail.dat – Microsoft Hell

Microsoft WindowsIssue: Have you ever received a “Winmail.dat” attachment?
I have clients who send files like Word or Visio via email but all I get is a “Winmail.dat” file. Argh! This issue is only like ten years old… Thanks Microsoft!@

When you receive a Winmail.dat file in place of an attachment it means the sender is using Microsoft Proprietary email formatting in their Outlook or Outlook Express email client or their outgoing Exchange email server is set to do so. Usually the culprit is the senders MS email client is set to send email in RTF “Rich text” format.


1) Sender changes their Outlook “Compose Messages” option to Plain Text or HTML (RTF is silly, use HTML!)

2) Exchange Server Admin adjusts server settings

3) And for the Winmail.dat attachments you already have… You can do the work Microsoft has placed at your feet and run any of these app / solutions to decode the dat file and view the contents:

Online service to decode Winmail.dat