On the Outlook blog, Jeremy Perdue writes:
Now consumers can use Outlook for free on macOS, no Microsoft 365 subscription or license necessary. Whether at home, work or school, Mac users everywhere can easily add Outlook.com, Gmail, iCloud, Yahoo! or IMAP accounts in Outlook and experience the best mail and calendar app on macOS. The Outlook for Mac app complements Outlook for iOS – giving people a consistent, reliable, and powerful experience that brings the best-in-class experience of Outlook into the Apple ecosystem that so many love.
I haven’t used Outlook, but Tonya uses it in her work at Cornell and says it’s a capable app for email and calendaring. That said, SpamSieve author Michael Tsai points out that this free version—which he sees as a free tier of service—is ad-supported and requires the “New Outlook” user interface that has attracted criticism. Microsoft 365 subscribers don’t see ads and can revert to the previous interface using Terminal.
Another thing to consider before testing Outlook is that the app asks you to sync all your data to the Microsoft Cloud to enable features that are otherwise limited to Microsoft 365 subscribers or Microsoft Exchange Online accounts. (I think you can decline using the Sync Directly with Google link in the dialog below, but I couldn’t tell what happened afterward. I ended up going into my Google Account and revoking permissions from Microsoft.) It’s not that I don’t trust Microsoft—the company manages email for hundreds of millions of users—it’s that replicating all my data in another online location feels like adding an unnecessary point of vulnerability from a privacy and security perspective. I suppose it could be viewed as a backup, but if that’s the goal, I would back up locally instead of to another cloud location.