I work with people who prefer Outlook as their primary email client. Occasionally, they will store copies of important emails to our company’s file server in the Outlook file format with a *.msg file extension. To open these Outlook files in Thunderbird, I use a pure Ruby program called mapitool, which is able to convert my_import_email_message.msg to my_import_email_message.eml.
To use the tool, you will need to install the ruby-msg gem, which will
install a new program called
$ gem install ruby-msg
To convert the fictions email message above, I would execute the following command.
$ mapitool -i my_import_email_message.msg
Mapitool will create a new file with the *.eml extension, which I can now open directly in Mozilla’s Thunderbird email client.