Confused Communication Masks a Simple Message About Retirement of Legacy Outlook Clients

Microsoft’s ability to communicate a clear and concise message about software retirements was demonstrated once again by the publication of message center notification MC801980 on June 14, 2024. Titled “Legacy Outlook clients retirement plan,” the post stated:

“Starting in mid-July, for organizations that use vanity domains and their users are on the following version of clients they will experience functionality diminishing:

• Outlook for iOS versions prior to 4.2411.
• Outlook for Android versions before 4.2342.
• Outlook for Mac versions older than 16.73.
• Windows Mail and Calendar applications.”

Copilot for Word required several attempts to rewrite the introduction into comprehensible English. In a nutshell, Microsoft is encouraging people using legacy Outlook clients to upgrade to a more modern version. The suggested versions are:

• Windows Mail and Calendar: the new Outlook for Windows (aka Monarch). Microsoft says that millions of consumer users have already made this switch. Support for these apps terminates at the end of 2024.
• Outlook for Mac: The current version is 16.86.
• Outlook for Android and Outlook for iOS; Build V4.2422.0 is the latest.

MC801980 announces the retirement of OWA light. The news about retirements of legacy Outlook clients caused some fuss and bother. In reality, the announcement is directed more at consumer users than Microsoft 365 organizations, but there is some detail to note.

Upgrade to a Modern Browser Now (Please)

From mid-August 2024, Microsoft will insist that people using OWA or Outlook.com use a recent version of their favorite browser. Internet Explorer is listed, but that doesn’t concern Microsoft 365 users because support for IE terminated on August 17, 2021. Most Microsoft 365 users will have a recent version of a browser on their workstation, so the advice to upgrade from Chrome or Edge version 79 (I’m running Edge version 125.0.2535.92 on my PC) indicates that there must be many Outlook.com users with old software.

The Demise of OWA Light

Microsoft announced some of the news (like the retirement of OWA light) in a technical community post on June 11, 2024. OWA light goes back to the earliest days of browser support for Exchange Server and is still available in Exchange Online (Figure 1). At one time, OWA light was important for low-end devices, but the need has declined over the years and its loss shouldn’t be of huge concern.

Some people use OWA light for accessibility reasons. Microsoft says that the latest version of OWA contains accessibility options, so the need to support a separate client no longer exists. For Exchange Online, Microsoft will remove the IsOptimizedForAccessibility parameter for the Set-CASMailbox cmdlet. Once a tenant is refreshed with the change (from mid-August to late October), mailboxes configured to use OWA Light will see an error page. Losing OWA Light might turn out to be the biggest impact on Microsoft 365 tenants signaled in MC801980.

In the technical community post, Microsoft also announced the termination of basic authentication support for Outlook consumer accounts on September 16, 2024. Taking the two communications together, a consistent message emerges that Microsoft wants its consumer base to move to modern software if users want to connect to its cloud services. It’s exactly what happened in the enterprise space, so this development is no surprise. Modern clients all support modern authentication, so that’s a good reason to upgrade.

Retirements of Legacy Outlook Clients Begin in mid-July 2024

Overall, there’s really nothing more in MC801980 than a call for people to replace old software with newer software. There’s no reason to panic and no need for people to upgrade their Outlook classic clients. The new Outlook for Windows has still not reached general availability. Even when it does, Microsoft says that Outlook classic will remain supported until 2029.

Microsoft will begin the retirement process for the older clients in mid-July 2024 and expect to complete the roll-out by late September 2024. No guarantee can be made about when a block will descend on consumer users or a specific Microsoft 365 tenant, so the call to action is clear: check your software and upgrade as necessary blocks start to descend in mid-July.

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