Using New Outlook on Windows for personal email, calendar, and contact management
I'm the 365/Exchange admin where I work. I left that setting enabled. It's to protect users. I don't care if my users scream and cuss at me. So far no one complains, btw. They don't understand the feature is there to flag phishing/spoofing email. It is sender's responsibility to fix their domain DNS records (DMARC, SPF, DKIM) so they won't be detected as unverified.