In this guide · 7 sections
Short answer
Switch most staff to new Outlook if they use mail, calendar and shared mailboxes. Keep classic Outlook for anyone who depends on COM add-ins, VBA macros, voting buttons, custom forms or full offline and PST work. Microsoft says classic stays supported until at least 2029.
New Outlook vs classic Outlook in one view
Classic Outlook is the long-standing Windows desktop program with a File tab at the top left. New Outlook is a newer app built on the same design as Outlook on the web. Microsoft's tip for telling them apart: if the top bar shows only the Outlook icon, it is classic; if the product name sits next to the icon, it is new Outlook.
New Outlook
Default for most business plans- Same layout as Outlook on the web
- Undo send, schedule send, snooze and pinned messages
- Web add-ins only; no COM add-ins or VBA
- Partial PST and offline support
Best for: Staff who mainly use mail, calendar and shared mailboxes.
Classic Outlook
Supported until at least 2029- COM add-ins, VBA macros and custom forms
- Full PST import, export and archiving
- Full offline cached mode
- Rules import and export, voting buttons
Best for: Users tied to desktop add-ins, macros or local data files.
What businesses lose in new Outlook
These gaps come from Microsoft's feature comparison between new and classic Outlook, as listed in October 2026. Microsoft updates the page as features ship, so check it before deciding.
| Feature | Classic Outlook | New Outlook | Who it affects |
|---|---|---|---|
| COM add-ins | Available | Not supported | CRM, document management, e-signature and older desktop plugins |
| VBA macros | Available | Not supported | Anyone running custom scripts |
| Custom forms and voting buttons | Available | Not supported | Approval workflows built on Outlook forms |
| .PST support | Available | Partially available | POP users and anyone with archive files |
| Offline support | Available | Partially available | Staff who work without internet for long stretches |
| Rules | Available | Partially available; import/export not supported | Heavy rule users |
| Quick Steps | Available | Partially available | Power users |
| Public folders, search folders | Available | Partially available | Older shared setups |
| Shared mailbox delegate access | Available | Partially available | Assistants managing someone else's mail |
| Access files on a network share | Available | Not supported | Attaching files from an office file server |
The add-in gap matters most. A COM add-in is code that runs inside the classic Outlook program on your PC; new Outlook has no such program, so there is no setting that turns it back on. Ask each vendor whether they offer a web add-in that works in new Outlook, and test it before switching anyone who depends on it.
What businesses gain in new Outlook
New Outlook is not only about removed features. Microsoft's comparison lists several that classic Outlook does not have:
- Undo send, schedule send and snooze for email.
- Pinned messages and favourites for groups, people and categories.
- Edit this and all following events in a recurring meeting series.
- Work hours and location on the calendar, and in-person event scheduling.
- The same layout and settings as Outlook on the web, so staff moving between a PC and a browser see one interface.
- Gmail, Yahoo, iCloud and IMAP accounts alongside work accounts, plus POP support.
Shared mailboxes, which many small businesses use for addresses like info@ or sales@, are listed as available in new Outlook, both as shared folders and as separate accounts. Our guide to shared mailboxes, groups and helpdesks explains which to use for a team inbox.
Microsoft's timeline: is classic Outlook going away?
Microsoft's migration stages page (updated February 2026) describes three stages:
| Stage | What happens | Notice Microsoft promises |
|---|---|---|
| 1. Opt-in | New Outlook is off by default; users try it with the toggle and can switch back | Current stage on that page |
| 2. Opt-out | New Outlook is on by default; users can still go back to classic | At least 12 months before it applies to managed Enterprise plans |
| 3. Cutover | Users cannot switch back; new Microsoft 365 deployments get new Outlook | At least 12 months before Production rings |
The same page says existing installations of classic Outlook, through perpetual and subscription licences, will be supported until at least 2029.
Small businesses are further along than that table suggests. Microsoft's switch to new Outlook page says that since January 2025, classic Outlook users on the Current Channel with a Business plan (such as Microsoft 365 Business Standard) are switched automatically after a series of in-app notifications. They can switch back with the toggle, and users or admins can turn the automatic switch off. That is why many staff suddenly find their Outlook looks different.
How to choose per user
You do not need one answer for the whole company. Both apps can be installed side by side, and Microsoft recommends running them together where people still need features that rely on classic Outlook.
List each person's add-ins and macros
In classic Outlook, check File > Options > Add-ins. Note any COM add-ins and any VBA macros. These people stay on classic until the vendor has a web add-in.
Check who uses POP, PST files or long offline work
POP users and anyone with archive PST files should stay on classic, or move to a cloud mailbox first.
Move everyday users to new Outlook
Staff who use mail, calendar and a shared mailbox can switch. Show them undo send and where settings now live.
Rebuild rules if needed
Rules import and export are not supported in new Outlook. Recreate important rules in Outlook on the web, where they run on the server.
Decide on the automatic switch
If some users must stay on classic, untick Automatically switch me to new Outlook under File > Options > General, or have your admin turn the switch off.
Revisit the list every few months. Microsoft has been marking features as available on its comparison page through 2026, so a blocker today may be gone by your next check.
Do it yourself or get help?
For a small team on Microsoft 365, choosing per user is a half-hour job with the steps above. If you are still deciding which mail platform to standardise on, our Microsoft 365 vs Google Workspace comparison sets out the trade-offs.
If an add-in has stopped working, rules have gone missing or someone needs PST mail moved across, a Quick Fix (1 hour) (S$119) sorts out one user's Outlook remotely, including switching versions, rebuilding key rules and checking shared mailbox access.
Frequently asked questions
Not yet. Microsoft's migration page describes three stages, opt-in, opt-out and cutover, with at least 12 months' notice before the later two reach managed enterprise customers. It says existing installations of classic Outlook, through perpetual and subscription licences, will be supported until at least 2029.
Yes, during the current stages. Use the toggle in new Outlook, or choose Go to classic Outlook from the Help tab. To stop being moved again, untick Automatically switch me to new Outlook under File, Options, General in classic Outlook. Admins can also turn off the automatic switch for the whole organisation.
New Outlook supports only web add-ins. Microsoft's feature comparison lists COM add-ins, the Outlook Object Model, VBA macros and custom forms as not supported. Ask the add-in's vendor whether a web add-in version exists; if not, keep that user on classic Outlook.
Partially. Microsoft lists PST support as partially available: new Outlook can open PST files and now import and export mail, calendar, contacts and tasks, but some classic capabilities are missing. Opening a PST needs classic Outlook installed with the same 32-bit or 64-bit architecture, and is not supported on ARM PCs.
Microsoft says that since January 2025, classic Outlook users on the Current Channel with a Microsoft 365 Business plan are switched to new Outlook automatically after a series of in-app notifications. You can switch back with the toggle and turn off the automatic switch in classic Outlook's options.