Microsoft to Block OWA Premium for Unsupported Browsers in Fall 2023

Run the Edge, Chrome or Firefox Browsers on Windows or Get OWA Lite

On June 2, 2023, Microsoft published an “initial communication” to inform Microsoft 365 tenants that they plan to redirect OWA connections created with unsupported browsers to use OWA Lite instead of the expected OWA Premium client. Microsoft says that they’re making the change to align OWA with the requirements for minimum browser support for other browser-based Microsoft 365 apps introduced earlier this year (MC518729, updated February 27, 2023). The changes announced in MC518729 affect apps like the Teams browser client and are due to take effect in July 2023.

OWA Lite

OWA Lite is a version of the browser client created for the on-premises versions of Exchange Server that still looks like the kind of email client you’d see around the year 2000. The client hasn’t changed much since its creation and is much simpler than OWA Premium. Although you can manage a mailbox with OWA Lite, don’t expect support for functionality like access to shared mailboxes.

In its place, OWA Lite can be useful. For instance, over a low-bandwidth connection, OWA Lite (Figure 1) consumes less network resources than the premium version does. I’ve even used the OWA Lite client on a Linux-based TV to create and send a few messages.

OWA Lite connected to an Exchange Online mailbox
Figure 1: OWA Lite connected to an Exchange Online mailbox

Another reason to use OWA Lite is when people have accessibility needs. The premium version of OWA is in an ever-changing state as Microsoft adds new features and tweaks the UI to prepare for the introduction of the new Outlook for Windows client (code name Monarch), which is based on OWA Premium. I’ve called Monarch a slightly prettier version of OWA, but because its UI is evolving, using the client can be hard for those who depend on client UIs being predictable.

Accessing OWA Lite

There used to be an option in OWA settings to select OWA Lite for a mailbox that seems to have disappeared. To test OWA Lite, connect to Exchange Online with the URL To revert and return to the Premium client, use

Supported Browsers

Supported browsers for OWA Premium with Exchange Online include Microsoft Edge, Chrome, or Mozilla Firefox on Windows 11 and 10. For macOS, Safari is on the list. Curiously, there’s no mention of the Brave browser, which is based on Chromium like Edge and Chrome. It might be that some of the bits that Brave removes from the Chromium engine create some difficulties for OWA. I have never had any issues using Brave with OWA premium, but that doesn’t mean that I’ve never encountered some lurking problems with the browser. Opera is another common browser missing from the supported list.

Restriction Starts in September 2023

Microsoft says that they plan to roll out the change to targeted release tenants in September 2023 and complete the worldwide deployment in November 2023. After the code update to impose the restriction arrives in a tenant, users who attempt to use an unsupported browser will get OWA Lite.

Forcing people to use OWA Lite and being unable to switch to OWA Premium with a user’s preferred browser is likely to be the source of disruption, annoyance, and help desk calls if users do not receive warning to switch to a supported browser. Microsoft minimizes the difficulty of the situation by bluntly saying that tenants should check browsers in use and arrange for upgrades to make sure that users “can utilize the full set of features from Outlook on the web.” Just another thing to add to the to-do lists of tenant administrators.

So much change, all the time. It’s a challenge to stay abreast of all the updates Microsoft makes across Office 365. Subscribe to the Office 365 for IT Pros eBook to receive monthly insights into what happens, why it happens, and what new features and capabilities mean for your tenant.

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