I loved Unibox because it grouped email by contact - this fit my workflow way better than grouping chronologically or by thread. It was not sorted by “from” but rather the main view was just contact names and clicking on the name would show a list of emails. It was so great. Much like other message apps. I only stopped using it - years after the developers stopped updating it - because I was worried about a future OS update breaking it.
Does Thunderbird or any other mail client do this? My memory from a billion internet years ago is that the UI is similar to all other email clients, especially Apple mail.