New Outlook

The new Outlook for Windows is the web-based desktop client Microsoft is progressively rolling out to replace classic Outlook for Windows (the long-running Win32 application). It shares the codebase with Outlook on the web (OWA) and the new Outlook for Mac, talks to Exchange Online via Microsoft Graph rather than MAPI, gets new features first (Copilot, Loop integration, faster updates), and is enabled by default for new Microsoft 365 users. Classic Outlook remains supported on a defined timeline; classic-only features (COM add-ins, VBA macros, certain shared-mailbox edge cases, PST flexibility) keep some heavy users on classic for now. Long-term direction: new Outlook everywhere.

Worked example

A company rolling out new Outlook company-wide finds one department — the executive assistants — can't switch yet, because a business-critical scheduling macro built years ago in VBA has no equivalent in the new client, which doesn't support VBA at all. IT keeps that department on classic Outlook while migrating everyone else, and separately opens a project to rebuild the scheduling macro's functionality using Power Automate or a supported add-in, so the assistants aren't permanently stuck on the client Microsoft is phasing out.

Common pitfalls

Assuming new Outlook is a like-for-like replacement and switching an entire organisation over in one weekend is a common rollout mistake — any team relying on classic-only features (COM add-ins, VBA macros, certain PST import/export workflows, some shared-mailbox edge cases) needs those dependencies identified and addressed before the switch, not discovered afterward. Confusing new Outlook for Windows with Outlook on the web is an easy mix-up since they share a codebase and look similar — new Outlook is still a distinct installed desktop application with offline capabilities OWA doesn't have, not simply a browser tab. And treating the "new Outlook toggle" some users still see as a permanent opt-out ignores that Microsoft's own stated direction is new Outlook eventually everywhere — planning migrations proactively avoids a forced, less-controlled cutover later.