First Yes, we know you can select the copy option when selecting Right-Click Move option, but you are not able to quickly send later files as a copy to the most recent folder list that Office365 lists.
Change the Right-Click option to Move/Copy
In the following menu, replace Move and Copy options with Search (instead of Move and Copy options).
Leave the recent folder list where it is.
Add a dialogue that asks if you want to move or copy.
Add a small icon to appear in the original message that shows it was copied (not needed if moved as um it would be moved lol).
This way users can first search for a folder or select from the recent and then select whether they want to Move or Copy.
In our business, this would allow for messages to be stored in client folders as well as allowing the sent folder to be searched quickly as well as allowing us to confirm which items had been copied. We copy instead of moving to ensure we do not miss billing for quick emails etc.