Not a full answer...but hopefully helpful...
If I drag an email from Outlook to my desktop, a .msg file is created.
I can then put that .msg file in a container.
If I drag the email straight from Outlook...it goes into the container showing text.
Looks like your container option is "file"...and the work to do is how to put it in there...
that works on Mac and Windows but not in FM Go (there is no desktop)
So true. I missed the FMGo reference that was staring right at me...sorry.