The end of classic Outlook for Windows is coming. Are you ready?

Microsoft prepares to replace an old faithful with something shiny, new, and lacking key features. Sound familiar?

Analysts have warned that some enterprises have a mountain to climb ahead of Microsoft's planned phase-out of the classic Outlook for Windows. 2029 is the earliest cut-off date for support, but some key functionality is still missing from the veteran app's replacement.

With its email, calendar, task, and contact functionality, Outlook has been around for decades. It is a favorite within enterprises, thanks partly to the ease with which the app can be extended. Knocking up a quick COM (Component Object Model) add-in to implement a company process was a simple task, and line-of-business applications needing Outlook integration could do so via an add-in.

However, Microsoft has warned that those days will be coming to an end and, last week, spelled out when the transition will occur to the new Outlook for Windows. Support for what Microsoft calls "classic" Outlook for Windows will continue until at least 2029.

The problem enterprises face is that the new Outlook for Windows does not have all the functionality available in the classic edition. Skype users faced the same issue when the classic version of the comms platform was deprecated. When it comes to new Outlook, functionality such as offline support might be rolling out, but other functions, including POP3 account support and support for PST files, remain "in the works," according to Microsoft.

COM add-in support is conspicuously missing from the list. Directions on Microsoft analyst Mary Jo Foley noted that Microsoft's take was that such add-ins "are often unstable and don't work cross-platform."

According to Microsoft, the solution for companies that depend on those COM add-ins for workflow and line-of-business applications is to look at the web add-ins platform. Foley said: "Microsoft officials maintain that most great add-ins are not just COM-based and exist in other formats, but not all customers seem to buy that claim."

Unsurprisingly, integration with Copilot and Teams has already hit the new Outlook for Windows, and Teams Chat is currently rolling out.

Movement of the people

The timeline for the cutover to the new Outlook for Windows has started, with users offered the option to opt in and try out the new service. Once the service has moved out of preview, Microsoft plans to make it the default – giving customers at least 12 months' notice of the change. After at least another 12 months, Microsoft will remove that option to opt out.

There are plenty of ifs and buts about the timelines, but it seems likely that the cutover will occur in 2025. Microsoft has said it will continue supporting the classic version of Outlook until at least 2029.

Direction on Microsoft analyst Rob Helm warned: "Outlook classic could disappear from Microsoft 365 Apps for Enterprise — the one you get with Microsoft 365 and Office 365 subscriptions — any time. Versions of that only live around 14 months, so that could be your lead time for migrating off classic Outlook."

Companies like Slack would insist that email's time has passed and that messaging platforms are the rage. However, although it is wielding the axe for COM add-ins, Microsoft is taking a more cautious approach to email.

"Some companies might want the new Outlook," said Helm, "I believe Microsoft is going to use it to quickly shim in newer collaboration technologies like Loop and Teams for the huge base of Outlook users, and some of Microsoft's customers see those technologies as the long-term replacement for email.

"But Microsoft's announcement shows it sees that as a very long term plan." ®

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