I have continued to use New Outlook as far as the mail part is concerned. Once you get used to it, it offers just a bit more than W10 Mail. Even the left mouse button for corrections works handy over time because there is a separation between correction and copy/paste. As previously reported, I use New Outlook for two IMAP accounts and it works well. Although New Outlook does not sync at all with my OneCalendar App, mail syncing with the Samsung Mail App is better than with W10 Mail mail.
The problem with "read mail" also occurs with me. If a mail is opened and read in the inbox, after moving it to "deleted" or an archive folder, it is often reactivated as unread.
My conclusion is that New Outlook is usable, once you get used to it, but certainly not a productivity platform that Microsoft claims it should be.