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Exchange Server Retires OWA Light Client in August 2026
On July 8, Microsoft announced the retirement of the OWA Light client from Exchange Server. The change will become effective in an update for Exchange Server SE in August 2026. After the update is installed, Exchange on-premises users must use OWA.
History of OWA Light
Microsoft introduced the OWA Light client in Exchange Server 2007. Exchange had included a web client since Exchange 5.5, but one of the longstanding truths about Exchange and other on-premises servers at the time was the reluctance of enterprise customers to upgrade servers and clients. Microsoft could push forward to build web clients based on the latest advances in HTML and JavaScript, but unless users ran a modern browser (defined as IE6 or IE7 for Exchange 2007), they couldn’t use the latest version of OWA.
The OWA Light client was Microsoft’s solution to extend OWA’s reach to devices running non-Microsoft browsers or older versions of Internet Explorer, including Mac workstations. It also answered a need for customers who disabled JavaScript due to security concerns. Essentially, OWA Light delivered a client that could run on almost any platform. In doing so, OWA Light extended the reach of Exchange to all manner of surprising platforms. I recall using OWA Light to connect to Exchange Online using an embedded Linux browser running on a TV in a hotel in Abu Dhabi in 2013. Although the experience wasn’t fast or optimal, I was still able to read, create, and send email.
Time moves on and the need for OWA Light gradually lessened. Exchange Server is now only available on a subscription basis and customers are forced to keep servers and clients updated. Microsoft dropped Internet Explorer years ago and the Edge browser adopted Chromium as its basic engine. Network connectivity is much easier and more capable today than it was in 2006. Browser standards became better defined and more widely used. And most of the on-premises market moved to Exchange Online, which requires connections using recent browsers.
OWA Light in Exchange Online
OWA Light was one of the components inherited by Exchange Online from Exchange Server. It remained in place from 2010 as an option that could be controlled on a per-mailbox basis through OWA mailbox policies. Switching a mailbox to a policy that involved OWA Light instead of the premium client was a somewhat childish if amusing thing to do to colleagues.
In 2023, Microsoft decided that OWA Light in 2023 should be the fallback for unsupported browsers. In other words, if you used an unsupported browser, you could only use OWA Light. That tactic didn’t last long because the Outlook team decided to retire OWA Light from Outlook.com in August 2024. That announcement didn’t explicitly refer to Exchange Online and I have been unable to find any other Microsoft statement confirming the retirement of OWA Light for Exchange Online.
However, there’s no mention of OWA Light in the Exchange Online service description and I cannot make OWA Light run by enabling the option in an OWA mailbox policy. Curiously, it’s still possible to create a new OWA mailbox policy through the Exchange Online admin center that blocks access to the premium client and sets the OWALightEnabled setting to true (Figure 1).
Assigning an OWA mailbox policy that disables the OWA premium client doesn’t do anything because Exchange Online only seems to use the OWA premium client. That is, if you use a supported browser. Overall, the evidence suggests that the June 2024 announcement covers both consumer (Outlook.com) and Exchange Online accounts. I can’t find any evidence that the retirement discommoded Exchange Online customers.
But On-Premises is Different
A lesson learned from Exchange Online cannot be necessarily applied to Exchange Server. The cloud environment is, by necessity, more homogenized. Even so, I don’t think that the retirement of OWA Light from Exchange Server will cause significant customer disruption. Organisations still depending on a very antique and limited client should already have identified those dependencies when Microsoft retired the client in Exchange Online. The biggest challenge might be finding the odd browser that never quite moved on from the mid-2000s, like that Linux-based TV browser in Abu Dhabi.
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