Should we move to new Outlook now or stay on classic?

Microsoft has been pushing new Outlook hard since 2024 and committed to supporting classic Outlook in 365 context through at least 2029, no hard end date beyond that, but in 2025 new Outlook still misses features that classic users take for granted. For SMB teams the choice is rarely binary, you sit in both for a while. The key is knowing what you give up and when you switch.

Try this first

1. 1List what your classic users do daily: COM add-ins (older CRM, legal tooling), shared mailboxes in cached mode, PST archives, complex rules, side-by-side shared calendars, MAPI properties via a custom add-in. Many of these don't work, or work only partially, in new Outlook.
2. 2Pilot new Outlook with a small group (one per department). Let them work in parallel for two weeks and keep a pain-point list. The toggle sits in the top of classic Outlook.
3. 3Decide per use case: people only in mail and calendar without heavy add-ins can often switch now. Power users with PST and COM add-ins stay on classic for now.
4. 4Communicate that this is a temporary split, not a preference. Otherwise colleagues will argue about who has the right version.
5. 5Plan a re-evaluation every 6 months, because new Outlook keeps getting features. What blocks you today is often solved half a year later.

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