A friend has recently sent me a Microsoft Word attachment that arrived in my mailbox as winmail.dat, which I am unable to open. Janet
Winmail.dat files were created by Microsoft to carry formatting information for "rich text" email messages. They are in Transport Neutral Encapsulation Format (TNEF). The best way to deal with the odd winmail.dat file is to upload it to tud.at/php/tnef, which will convert it for you. If you get lots, you could download TNEF (tnef.sourceforge.net) and do it yourself.
Incidentally, I answered this question more fully in September 2001. However, I was unable to find it on any search engine, even though I knew exactly what I was looking for.
Backchat: Paul Beam says he uses Winmail.dat Reader, a free utility from http://www.kopf.com.br/winmail/. He writes: "I have it installed, and can read winmail.dat attachments by double-clicking on them in Thunderbird." Lesley White mentions WMDecode from Biblet Computer Services (http://www.biblet.freeserve.co.uk/). The Windows version costs $10.
