It's just not very nice is it? If I had to say which version was the improved, futuristic version of the other I would say the Outlook desktop program is light years ahead of Outlook online. MS XL is particularly bad for this, especially for accountants, who presumable are major users of the program. One significant issue is features available on the desktop versions of apps are simply not available on the web versions. As a long time user of MS Office programs I have found the move to internet based systems to be very frustrating. If it's limited to the UWP Mail app, then they can do whatever they want with it, I don't care much. They better not try this again with Office Outlook. It is now called THE 'OneNote', so it must be here to stay. This is why enterprise and people like me did not allow Microsoft to kill Proper OneNote with this inferior version.

As far as UWP apps go, it's decent, but compared to a proper Office OneNote it is still inferior. I have tried UWP OneNote, as have many others. It supports Addins and has better Office integration (naturally). The customisation of the whole UI is better on Office Onenote, I can move all the navigation panes all over the place. UWP OneNote lacks offline notes, which is very important in the enterprise sector, it lacks customisable title bar, which is part of every office app (even Mac OneNote has that, come on!) The amount of settings on UWP is laughable. I really dislike the single-line ribbon, it almost defeats the purpose of a ribbon (I always enable full ribbon on web apps, but UWP OneNote has no such option. They did that as part of Desktop version's resurrection. The syncing engine has been moved to Office OneNote too, so that's not an advantage any more.

How to get microsoft outlook on mac