The biggest thing about Outlook is the fact that I can search my inbox for the last 20 years. Mail.app has forgotten how to do that despite "all mail" being set to download. My host is Office 365 for all of my inboxes + 1 iCloud inbox. So maybe it's just that a 1st party experience is superior here? Mail for Mac is still okay but with my new job being Office 365 (previous was Gmail), I'll probably go Outlook on desktop too