view Opera mail in File Explorer preview pane
bpm2 last edited by
I came across this today: https://www.winhelponline.com/blog/eml-file-preview-pane-explorer-windows/, checked to see if MBS is on the utility's list of supported types - and it is.
You click a box, close the utility, & it makes a registry key for each selected filetype. Log out & back in - you'll see content of MBS files when you hover them in their folder.