From Traction Software:
WinMail Decoder Pro extracts attachments and email message from winmail.dat files with ease, simply drag and drop the winmail.dat on the WinMailDecoder.exe or with our new version you can run the Windows application and browse for a file/drag and drop and extract the files in a nice and easy usable interface. WinMail Decoder Pro consists of two programs, a DOS program and now a new alternative Windows application. When you receive a email message from another email client that has mistakenly or unknowingly sent you a message in Microsoft Outlook RTF format you will receive the normal message text along with an attached file named winmail.dat, The winmail.dat file contains a RTF file formatted version of the email message and attached files. Version 2.01 may include unspecified updates, enhancements, or bug fixes.