I used Lotus Notes in the 00s and 10s and greatly preferred it to Outlook. The full featured one, not the OWA version.

Yes, the UI was clunky, but it was quick. It was McMaster-Carr quick. The mail client was never a barrier between you and your emails. These days I miss Outlook, as the new web-based solution we replaced it with is even worse.

Just to add that nowadays once can use HCL Verse for web- or mobile app-based email access to their Lotus Notes email database. It's quite sleek and it works.