Occasionally I receive emails from people which have a single attachment named
winmail.dat. After a bit of searching online, it turns out that Microsoft Outlook, depending on how it is configured, uses the MIME type
application/ms-tnef for attachments, which other mail clients (e.g. Thunderbird) can’t read.
Unfortunately I couldn’t find a simple way to patch other mail clients to read these files, and the extension that was available for Thunderbird has not been updated for over 7 years and so is unlikely to work. However, someone has helpfully created a program for Linux called TNEF, with the source code available on GitHub.
Installation is relatively simple, I used the following steps:
git clone https://github.com/verdammelt/tnef.git cd tnef autoreconf ./configure --prefix=/home/paul/bin/tnef make check make install
To extract the files contained within
winmail.dat, save the attachment locally (e.g. to
/tmp) and then run:
tnef -f /tmp/winmail.dat -C /tmp/
It might be possible to automate the above steps so that Thunderbird calls
tnef with the appropriate options, but I haven’t had time to investigate that. Please let me know in the comments if you’re aware of an alternative option which would integrate with the latest versions of Thundebird (60.x).