Good Linux question — answering as the UphillTech team:
This is an MS-Outlook format. There is a command line tool called MSGConvert (see www.matijs.net/software/msgconv ) which converts .msg files into .eml. You can open those with Thunderbird or Evolution. On Ubuntu you should be able to install the tool using sudo apt-get install libemail-outlook-message-perl libemail-sender-perl from a command line. Use msgconvert *.msg to convert every file in a directory at once. MSGConvert will produce copies of your .msg-files with the suffix .msg.eml. Regardless, your friend should learn how to send content properly.
Full answer by Georg Jung: https://superuser.com/a/979603 (CC BY-SA 4.0).
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