I use Outlook at work and Mail (Microsoft Store app) at home. I suppose the main reason is that they have basically foolproof compatibility and functioning wit

I use Outlook at work and Mail (Microsoft Store app) at home. I suppose the main reason is that they have basically foolproof compatibility and functioning with their respective O365 and Outlook.com (formerly/via Windows Live Custom Domains) server counterparts. Functionally they have what I need. I turn off the Focused Inbox feature in both as I have no problem with a little tedium. The rules system in both is good, though that runs server-side technically. I turn off conversation view nowadays, but have used it extensively in the past with massive threads and found it quite good (Outlook). Outlook's list views can be customized quite extensively, and the dark theme is good. Search works fine in both clients. I have taken Outlook to somewhere around 100GB and over 1,000,000 emails back in the year 2013 and that worked fine. IIRC the OST was always 30-40GB, and I would shuffle things off to yearly archive PSTs.