What are Winmail.dat files and How Do I Open Them?

Sometimes an e-mail message might arrive in your inbox with a “winmail.dat” file attachment.  You might find that that you are unable to open it. Why does this happen?
Sometimes messages sent from the Microsoft Outlook e-mail client or Microsoft Exchange server have Rich Text Formatting (RTF) that your e-mail client does not understand. E-mails with RTF display different text styles, fonts and colors. The winmail.dat file contains the RTF information for the message, but usually will not open normally. 
Usually what happens is that your e-Mail client will display the message text, while the the RTF formatting remains in the Winmail.dat file attachment.  If you could open the RTF message, you would see email with the same text but different formatting.
You could ask the sender to only send to you in plain text formatting, and then there would be no winmail.dat file attachments.
Another option for Windows users (besides purchasing Microsoft Outlook) is to download a viewer program like MessageViewer Lite by Encryptomatic LLC.  MessageViewer Lite can display the contents an formatting of the winmail.dat file. MessageViewer Lite is us$24.95. A free 15 day trial is available.
MessageViewer Lite viewer opens winmail.dat files.
MsgViewer Lite, the Winmail.dat viewer for MS Windows.
MessageViewer Lite also opens Outlook .msg emails, and .eml email files, all in addition to Winmail.dat files.
If you have any questions, post them below and we’ll be glad to answer you.