Project Monarch or One Outlook to rule them all
You may have heard about ‘Project Monarch’, Microsoft’s plan for a single Outlook program for Windows, Mac and maybe other platforms. This is what we know so far about Microsoft’s ‘vision’ for ‘One Outlook’
Project Monarch is an early Progressive Web App (PWA) which will have email, contacts, calendar and perhaps other ‘Outlook-like’ features. In many years from now ‘Monarch’ may replace Outlook for Windows or Mac with a single PWA for both systems.
A Progressive Web App looks like a normal program but is really a complex web page running with browser technology behind it. Think of a web page (like webmail) but not in a browser tab.
Microsoft already has a limited form of Outlook PWA available see Install the latest Outlook as a standalone web app
Project Monarch now called One Outlook is available as a preview, see First look at the new Microsoft Outlook – One Outlook
There are links to download Project Monarch but they won’t get you far. Monarch can be installed but won’t work without an authorised mailbox (i.e. Microsoft staffers).
One Outlook
‘One Outlook’ is Microsoft’s ‘vision’ for a single Outlook program that runs on any platform – Windows, Mac, Linux or anything else that comes along.
Monarch is based on web technologies (Javascript, CSS, HTML etc) and should work on any device with a compatible browser (Microsoft’s Edge).
The benefits for Microsoft are clear. Development costs drop because they only have to build one app to work for Windows and Mac. Their Edge browser will get onto more non-Microsoft devices because it’s necessary for the Outlook PWA.
Of course, Microsoft will promote the advantages for customers with non-specific marketing drivel like ‘Faster, customer-focused innovation with consistent experience on all clients’.

The future
Outlook for Windows and Mac aren’t going anywhere soon.
Maybe preview releases in 2022 . There’s a LOT of work to be done before Monarch is ready to run alongside Outlook for Windows, let alone replace it.
The first public look at a Project Monarch like Outlook is due in 2022 targeted as a replacement for the Windows 10 Mail and Calendar apps.
For all of Microsoft’s ‘vision’ and promises, a full Outlook PWA to replace Outlook for Windows is sure to be a compromise. Assuming it happens at all.
Some features will be dropped and others changed. Outlook for Mac users will hopefully benefit more with the introduction of features they are currently missing.
Project Monarch and the ‘vision’ may all go up in a puff of smoke. Long time Microsoft watchers have seen projects like this dropped as the ‘vision’ and world changes. Maybe you remember Microsoft’s vision for all of Office to go platform-independent with Java – a lot of development money was spent on that project before disappearing.
First look at the new Microsoft Outlook – One Outlook
Install the latest Outlook as a standalone web app
Special tricks to add iCloud accounts into Outlook 365 for Mac
Make Microsoft Office a Progressive Web App or PWA
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