New location for the Mail, Calendar, People, and other modules

People certainly feel passionate about their navigation!  While I agree with most people on this thread that I hate this LeftNav design, I mostly hated that I couldn't change it.  Outlook has historically given us many options to optimize the layouts that it was annoying to not be able to choose.  I'm glad that you listened to your users and the feedback to give us the option to move it back, at least for now.

I have 2 points to make and some overall feedback:

1. What's the value I get for adjusting to the change?  People will always hate it when you change something they're comfortable with (remember the introduction of the Office Ribbon?). Sure, it's meant to feel more like Teams but Teams is a relatively new application and not one that people have been using for years.  There's just not enough value in what is offered in the new design to get people over the change.  When, and if, there are more apps that people want and need to use, that could make the real estate (and change) worthwhile; but there just isn't right now.  I personally use keyboard shortcuts to move between Mail, Calendar, and Contacts and don't use anything tasks or notes (or journals when that was a thing) so the real estate it takes is even less worthwhile for me.
2. Stick with it.  The LeftNav design is more modern and at some point, people will have to get over it.  Despite the ranting and raving, they will eventually--like we got over the Office Ribbon and the Windows Start menu.  I don't agree with some of the comments like, "How dare you change my UI?"  If we didn't modernize UIs, we'd all still be using green screens.  I just think the LeftNav design requires more overall thought (see feedback below).

Feedback

• I would've liked to have seen an option to collapse the LeftNav and maybe move it into a hamburger menu.  You already have something similar when collapsing the folder pane which moves the navigation options into a LeftNav--albeit with the folders, which I would like to keep expanded.  You also have real estate for the hamburger and something similar with the Quick Access Toolbar.  Collapsing into a hamburger and opening the LeftNav when clicking on it (instead of an expanding menu) could also help people get used to the idea of the LeftNav.
• I hate when apps overindex on iconography, especially when introducing a new UI element.  While the icons for mail, calendar, people, and tasks are familiar, what is the blue check thing or the square thing with 4 squares in it (looks like the Windows logo)?  Just add the text of what the button is for (like in Teams, the Apps icon has "Apps" under it).
• There's such disparity with the LeftNav in the browser version of Outlook.  In the browser version, the LeftNav doesn't have Tasks but there's a mix of Outlook navigation (Mail, Calendar, etc.) and other Microsoft apps (e.g., Yammer).  There are some things in the LeftNav that are already in the global Apps menu at the top left, like Yammer and OneDrive and the Apps icon in the LeftNav has links to the Office apps but no option to see other apps.  There are also links to things like Teams calls and Chats in the global nav on the right.  There's no rhyme or reason to where things are and no cohesion; it all just seems oddly dispersed and indiscriminately redundant.
• Also in the browser version, there's no option to reorder or customize the LeftNav.  Why would I want Yammer in there?  Who even uses Yammer?  And Bookings?  What is that and why do I need that in my LeftNav?
• Interestingly, there's is a hamburger menu in the browser version, but it's for the folders and its behavior is weird.  It's always there but there's no visual indicator as to whether the folder list is collapsed or expanded and see above for comment about just showing text.  The desktop version has right and left carets to expand or collapse.  Also, I'm used to hamburgers for expanding things so it's a weird icon to use for completely hiding and showing a pane.  The MouseOver tip says "Collapse left pane" which is weird because the folder list is no longer the left-most pane.
• Oddly, I'm less bothered by the LeftNav in the browser version but not sure why.  My guess is that I don't use the browser version much and it's different enough from the desktop version that I already have to reorient myself whenever I use it anyway.
• Comparison to Gmail: Please let the LeftNav be a trend towards moving Outlook components like Calendar and People into some buried menu, the way Google has Contacts and Calendar all the way in their App Launcher.  I like that Outlook is my organizer; it has the things for me to go about my day and is integrated.