Mail on MBP 10.12.6 won't maintain chosen sort order of Mail

Mail will not maintain the sort order I prefer for Mail, Classic layout with Inbox and Sent Mail intermingled according to date and time order, newest at the top. Instead, it defaults to showing only unread emails when I open Mail. For a while I tried selecting ‘Sent’ then holding down Command and selected ‘Inbox’ which amalgamated them sorted into the preferred order. Now this doesn’t work.

Once upon a time I was able to select the order I wanted them to appear and it used that format every time mail was opened.

I’ve read several articles on-line but can’t find the answer. One I found said to select View> Options but that must be for an earlier version as I can’t see Options.

I’d appreciate some guidance.

Please? With only the incoming, unread, mail displayed It’s not possible to see at a glance who I’ve emailed, or quickly locate emails I’ve already read.

Not even ‘cc’ ing myself will keep them in the list, once they’ve been opened.

Does anyone have a suggestion, please, or can point me to a link. I can’t find this on-line.