Hi @Patrick O'SULLIVAN ,
According to my research, currently, the new Outlook for Windows does support working offline, this function is still under development, and it is coming soon. To learn more about the new Outlook for Windows, check out the following articles:
Getting started with the new Outlook for Windows
The new Outlook is not yet complete and some options may not be available or work as expected. You can switch back to the classic Outlook at any time by clicking the toggle button in the top right corner of the window.
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