If some messages arrive from the Internet looking like scrambled eggs, then you need to save each one as a file, then decode it. This is much less of a problem with current versions of Microsoft Outlook than it was with older versions of Microsoft Outlook and Exchange Messaging.
There are two types of files that may need decoded: uuencoded messages, that for one reason or another did not get decoded by Outlook and winmail.dat files that result from using RTF message format.
The TNEF/winmail.dat decoder tools can be used by non-Outlook users to "crack open" winmail.dat files to recover attachments.
Rot-13 Addin is Rot-13 encoder/decoder for Outlook.Free. Version: 18.104.22.168
Tool for Macintosh computers to decode the Winmail.dat attachment sent in Rich Text Format messages.
Winmail Opener is a small and simple utility that allows users to view and extract contents of TNEF-encoded messages (winmail.dat). Version 1.4 - Free.
Open, convert and save the files on winmail.dat email attachments sent by Microsoft Outlook and Exchange. Easy-to-use graphic interface (no command-line tool). Displays the original message subject and body. Free. Android version available.
Online utility to decode attachments sent by Outlook that arrive as Winmail.dat files because the message was sent in Rich Text Format format.
Includes UUencode, BinHex and MIME support, so you can extract attachments from messages that you've saved as files.
If other people complain that your messages arrive with gibberish or a mysterious WINMAIL.DAT file, see Outlook is sending winmail.dat attachments to Internet addresses