Microsoft Will Support Classic Outlook for Windows Until at Least 2029

This week, Microsoft revealed that it will support the classic version of Outlook for Windows through at least 2029, which should placate those commercial customers who are concerned about the lackluster quality of the new Outlook. That said, the new Outlook will soon reach general availability (GA), and when that milestone occurs, it will replace the classic app in new Microsoft 365 installs.

“Currently, the new Outlook for Windows is available for preview for commercial customers and is getting closer to readiness for General Availability,” Microsoft’s Margie Clinton writes in the announcement post. “The migration will be a multi-year journey delivering more capabilities in new Outlook, working with customers assessing feedback and readiness, and providing admin guides and tools to ensure customers have what they need to prepare accordingly.”

That’s been the plan all along, of course. But while we have known that the new Outlook would replace Mail and Calendar for consumers in Windows 11 sometime in 2024 for a while now, Microsoft has always been more vague when it comes to its commercial customers on Microsoft 365. And today, for the first time, we have a bit of clarity: Microsoft will use the same staged approach to deploying the new Outlook to commercial customers as it did with the new version of Outlook on Mac. And in doing so, it will “continue to honor published support timelines for [the] existing version of classic Outlook for Windows until at least 2029.”

That doesn’t mean that things aren’t about to change, however.

The new Outlook is currently in an opt-in stage in which customers see a “Try the new Outlook” toggle in the classic Outlook for Windows app and can give the new app a try and then return to classic Outlook if there are missing features they need. During this stage, customers can run classic and new Outlook side-by-side.

But the new Outlook will reach GA soon, at which point the new app exits preview and is fully supported. That’s when the clock starts ticking. And at least 12 months before it formally moves into the next stage, called opt-out, Microsoft will alert commercial customers to the coming change. When it does reach opt-out, the new Outlook will become the default Outlook experience and customers who wish to remain on classic Outlook will need to opt out manually. Microsoft says it will also provide commercial customers with tools so they can move their organizations to the new Outlook ahead of time if desired.

And then the clock begins ticking again: At least 12 months before it moves into the next stage, called cutover, Microsoft will alert commercial customers of that coming change as well. During this stage, new deployments of Microsoft 365 commercial will include the new Outlook, though existing installs will continue to be supported. And as before, Microsoft will allow organizations to move to the new Outlook ahead of the deadline if desired.

And then, in 2029 at the earliest, classic Outlook for Windows will be retired, and all customers will be expected to move to the new Outlook.

Microsoft has updated a November 2023 post describing the features it is working on implementing in the new Outlook ahead of GA. Some of the to-do items from then—like offline support, an outbox folder, Teams Chat, read receipts, and more—are already rolling out while some others—EML and MSG file support, folder reordering, and drag and drop emails and documents to the desktop—will ship this month. And others—PST file support, POP3 account support, and so on—are on less clear timelines. But the point here is that Microsoft will get the new Outlook into a state of readiness that’s acceptable to its commercial customers before just flipping the switch.