The new Outlook switch needs pilots, gap mapping and a controlled rollout

In most of the tenants I work with, the new Outlook switch is no longer something on the horizon. It's happening now. Organisations are working through opt-in and opt-out phases, and I keep noticing how much the experience depends on preparation, or the lack of it. Classic Outlook is still included in Microsoft 365 Apps for the time being, but many users now get the new Outlook by default, along with a toggle that's hard to miss. If you don't manage the rollout and the communication yourself, expect more support tickets and frustrated users as people find the toggle on their own.

The new Outlook is already rolling out and admins can manage the toggle

The question I hear most often is how long a company can stay on classic Outlook. That depends on your update channel, your tenant settings and the details in the latest Message Center posts. In many environments the new Outlook is offered as an opt-in. In others it's turning into the default. The timeline for a fully mandatory switch still varies, so check your Message Center and the current Microsoft 365 roadmap for what applies to your tenant.

You can control the toggle centrally through Group Policy or Intune. A dedicated policy shows or hides the new Outlook switch, and that's the setting to use if you want users to stay in classic Outlook while you run a pilot or document gaps. Several of my customers have done exactly this. They started with IT-savvy users or with teams that don't depend on legacy add-ins, and only then opened it up to more people.

Several feature gaps still matter in practice

The new Outlook is improving fast, but some differences from classic Outlook will disrupt workflows if you don't plan for them. These are the gaps I still run into most:

• COM add-ins: Only web add-ins are supported, so older integrations and VBA-based workflows often break.
• PST files: Local PST file integration isn't there yet, which can affect archiving and local backups.
• Offline support: Offline capabilities are still limited, because the client assumes a constant cloud connection.
• Shared mailboxes: Delegated and shared mailboxes don't behave quite the same as in classic Outlook yet.
• Macros/VBA and some third-party tools: A lot of customisations and automations simply don't run in the new client.

In larger or more regulated environments, I'd map features and dependencies before switching on the new Outlook widely. Skip that step and you end up with confused users or, worse, interrupted business processes. I wrote about this in detail in New Outlook for Windows: Enterprise readiness in early 2024, and several of those pain points haven't changed.

Group Policy and Intune give you control over the switch

You can manage toggle visibility and app defaults with on-premises Group Policy (ADMX templates) or with Intune device configuration profiles. In Intune the setting sits under Device configuration → Administrative Templates → Outlook → “Show the new Outlook”. In hybrid environments, Group Policy lets you target specific OUs or groups. I've also seen policies that only applied some of the time, which left a mix of clients and a few pilot users nobody had planned for.

Practical tip: Give your pilot groups a direct feedback form and log specific compatibility issues. You'll spot blockers early and keep the helpdesk quieter once you widen the rollout.

A staged pilot works far better than a big-bang switch

I wouldn't begin with a switch across the whole organisation. In enterprise projects I always pilot with a mix of teams, some with complex add-in requirements and some without. That surfaces the real blockers and gives you time to adjust documentation and helpdesk answers before you scale. Testing across release channels (Current Channel versus Monthly Enterprise Channel, for example) also shows you how features and fixes arrive.

This is the pilot process I typically use with customers:

flowchart TD
Start["Start pilot group"] --> AddinsCheck["Test add-ins & workflows"]
AddinsCheck --> Feedback["Collect feedback"]
Feedback --> Adjust["Adjust policies & docs"]
Adjust --> Rollout["Wider rollout"]

Figure: Staged rollout of the new Outlook client with repeated feedback rounds.

Classic Outlook stays for now, but the direction is clear

If certain features keep you on classic Outlook, plenty of others are in the same position. Classic Outlook will stay in Microsoft 365 Apps for the foreseeable future, and Microsoft hasn't announced a hard end date. Even so, Microsoft's messaging and the pace of development make it obvious that everything is heading toward the new Outlook. Migrating add-ins, training users and rethinking local archiving all take time, so don't keep pushing the preparation back.

If you want more detail, Microsoft's new Outlook admin overview and the documentation on controlling the install are up to date and useful in practice.

My advice is to define pilot groups, be open with users about the main feature gaps and keep the rollout firmly in your own hands. That saves you trouble and gives users a better experience. The classic client hasn't gone away yet, but the shift is well underway.