I can see several options:
1) Tweak Outlook VBO to open actual eml and read it. Sould work for both attached eml and file on disk.
2) Same thing with EWS - eml attachment is almost like regular message for the api.
3) Use 3rd party tools to open eml files:
https://askubuntu.com/questions/28135/how-to-open-eml-filesWhich way is better depends on vbo you use for mail and your final goal.
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Andrey Kudinov
Project Manager
MobileTelesystems PJSC
Europe/Moscow
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