We all know the problem and have had the frustration for years. My guess for the future is that when and if Microsoft converts Premium to the Edge browser, we all will be annoyed. The "new" Premium will be devoid of all we like about the "old" Premium, especially the mail setup.
Somehow I stumbled onto this process. When I open Mail & More, my mail is separated into three email accounts that I carry for convenience. Also, I have Outlook with it being associated with one of the three email accounts, my MSN email account. As I scan my Mail & More emails in the other two email accounts, anything I want to read I transfer to my MSN email account. Afterwards, I open Outlook and read the emails I put there in my MSN email account. Big time saver, gets rid of lots of stuff quickly that I don't care about. It's annoying, but works. I'm risk-averse, so I'm careful what I wish for - I might just get a Premium with Edge but lose all I like about Premium now.
I'm in with Premium until next January, then I'll decide whether to give up on Premium. (I said that last year, too).