New Outlook vs Classic Outlook: What Changed

New Outlook and classic Outlook are two different programs that share a name. New Outlook is the modern app Microsoft ships preinstalled on Windows 11, built on the same codebase as Outlook on the web. Classic Outlook is the desktop program from Microsoft 365, and Microsoft has committed to supporting it until 2029. The short version: new Outlook is lighter and consistent everywhere, classic Outlook is deeper and still the one that runs COM add ins, public folders and a proper offline store.

This is the comparison that decides whether you accept the switch, delay it, or leave Outlook entirely. All three are reasonable answers depending on what your mail actually is.

What is the difference between new Outlook and classic Outlook?

Classic Outlook is a native Windows application with thirty years of features bolted on: add ins, PST archives, public folders, macros, a local data store, and a settings dialog most people have never reached the bottom of. New Outlook is the web version of Outlook wrapped so it runs as a Windows app, which gives you one identical experience on Windows, Mac and in a browser tab, plus tighter Microsoft 365 and Copilot integration.

That architectural difference explains almost every disagreement people have about the two. The things new Outlook does better (consistency across devices, faster updates, a cleaner interface, lower memory use) come from being a web app. The things it does worse come from the same place.

New Outlook vs classic Outlook, side by side

Is new Outlook better than classic Outlook?

For a single Microsoft 365 mailbox on a machine that is always online, yes, and mostly because it is simpler. It starts faster, uses less memory, gets features earlier, and looks the same on your laptop, your Mac and the browser you borrow at a client site. If your relationship with Outlook is reading mail and accepting meeting invitations, you will probably prefer it.

For anyone whose workflow depends on the desktop program being a desktop program, no. That covers offices running a CRM add in, teams working out of public folders, anyone with fifteen years of PST archives, and people who genuinely work on planes and trains. Those are not edge cases, which is why Microsoft extended classic Outlook's support runway to 2029 rather than forcing the move.

What features are missing from new Outlook?

The list has been shrinking, which makes any answer worth checking against your own build rather than taking on faith. The gaps that have mattered most are COM add ins, which do not run at all and are replaced by a smaller web add in model; public folder support, which is limited; POP3, which was dropped outright; and full offline working, which was absent at launch and has been the most complained about item since.

PST support is the interesting one, because it shows how the gap is closing and what closing it costs. New Outlook can now work with PST files, but opening one requires classic Outlook to also be installed, and both have to be the same architecture, either 32 bit or 64 bit. That is a real feature rather than a promise, and it is also a strange thing to inherit: the modern app leaning on the old one to read the old format.

Can I still use classic Outlook?

Yes. If you have a Microsoft 365 subscription or a perpetual Office license, classic Outlook is still there and still supported through 2029. New Outlook has a toggle in the top corner to switch back, and on a managed machine your IT department can control which one launches by default through policy.

The caveat is that "supported" and "developed" are different words. New features are landing in new Outlook first, and in some cases only. So staying on classic is a way to protect a working setup for a few more years, not a way to avoid the migration. If you are the person who will eventually have to plan that move for a whole company, it is worth knowing what your Microsoft 365 subscriptions are actually costing you before you scope it, because licensing is usually the larger number and it is easy to find seats nobody has signed into for months.

How long will classic Outlook be supported?

Until 2029, per Microsoft's own commitment. That is a long runway by the standards of this transition, and considerably longer than Windows Mail got. Support for Windows Mail, Calendar and People ended on December 31, 2024, with no equivalent grace period, which is why so many people arrived at new Outlook without choosing it.

Does new Outlook work with Gmail and other IMAP accounts?

Gmail, Yahoo and iCloud connect over IMAP, so the common cases work. Two limits are worth knowing before you rely on it. Third party accounts receive lower priority than Microsoft ones, which shows up as a less complete feature set rather than an outright failure. And new Outlook does not expose manual POP, IMAP and SMTP server settings at all, so a mailbox on a small host, a shared hosting account or your own domain with unusual ports can simply refuse to set up, with no dialog anywhere to fix it.

That second limit is what pushes a certain kind of user out of Outlook entirely rather than between its two versions. If you need to type a host and a port, you need a client that has a box for a host and a port. Every email client for Windows in the wider field still has one, including Thunderbird, eM Client and browser based options like ours.

Is new Outlook just a web page?

Essentially, yes, and that is the design rather than an accusation. New Outlook is the Outlook web experience delivered as a Windows app, which is why it behaves identically on Windows, Mac and the web, and why it updates on a web release cadence instead of an Office one. The practical consequence is that most of what makes a native app native (deep local storage, arbitrary plugin code, working with the network off) is either limited or absent.

It is also worth noticing what this means for the wider argument about desktop mail. Once Microsoft's own flagship client is a web app in a window, the case that a browser based client is somehow less serious mostly evaporates. That is the reasoning behind our web based email client page, and it applies just as much to Outlook as it does to us.

Should I switch to new Outlook?

Work through it in this order. If you use COM add ins, public folders, POP3 accounts or a manual IMAP configuration, do not switch yet; those are the four hard blockers and none of them has a workaround inside new Outlook. If you regularly work offline, test that specifically in your own build before committing, because it is the gap that changed most recently. If neither applies and you mostly read a Microsoft mailbox, switch and enjoy the lighter app.

There is a fourth answer people reach less often. If what pushed you into this comparison is that you run four or five mailboxes across two providers and no version of Outlook handles that gracefully, the choice between old and new Outlook is not really your decision. That is a multi account problem, and it is worth reading what Outlook will and will not do for a unified inbox before you spend a weekend on either version.

What about Microsoft 365 work accounts and third party clients?

One change catches people migrating away from Outlook rather than within it. Microsoft finished retiring basic authentication for Exchange Online in April 2026, so a managed Microsoft 365 work or school mailbox no longer accepts a plain username and password from any client. Outlook itself is unaffected, since it authenticates with OAuth. A third party client needs OAuth support to connect at all.

Personal Outlook.com and Hotmail addresses are a separate case and still connect over IMAP with an app password. So do Gmail, iCloud, Yahoo and essentially every independent host. If you are shopping for a replacement client, that single question, whether your mailbox is a managed work account or not, decides most of the shortlist for you. Inboxes connects with an app password, which means personal and own domain mailboxes work and managed Microsoft 365 accounts generally do not, and we would rather say that here than let you find it out during setup.

The short version

New Outlook is the future of the product and it is already good enough for most single mailbox users. Classic Outlook keeps working until 2029 and remains the only version that runs add ins, public folders and a real offline store. Neither of them is built for someone reading five accounts across three providers, which is a different problem with a different set of tools. If that is you, our email client for multiple accounts page covers what that shortlist looks like.