This account is not supported in Outlook for Windows due to the license provided by your work or school

I'm sorry, but I don't agree with the argument posted here that suddenly EVERY mailbox must (seperately) be tied to a license with apps. Since when is that the case? A user could always before be in the situation where they paid for exchange online + desktop apps (e.g. 365 Business Standard) and then take out another domain with exchange online only, and add that mailbox to the same Outlook profile.

Of course, if you had used that single mailbox (without apps) on a device where there is NOT YET a licensed Outlook app, it would make sense. But we're talking about a use case where there is an existing, fully licensed Outlook, and people are just trying to add more (fully licensed) exchange accounts.

What's next? Is Outlook going to block adding Zoho mail because "they don't come with a license to use Outlook"? Or Google mail? It makes no sense. This issue started occuring when the new Outlook went from "preview" to "new" status. It's clearly something else.

I tested it just now. As soon as the mailbox itself isn't tied to apps (i.e. Outlook for Desktop) by virtue of a license that "includes" the desktop apps, you cannot add it. So, that basically means their entire Exchange Online (which seems to be mostly the Basic users) user base (where users previously were able to add their account to Outlook, let's say if they had a Home & Business license), they can no longer do so going forward. It doesn't matter if they already have a separate, valid license for Outlook. So, in my scenario:

* I already have Microsoft Office 2021 Home and Business. Which grants me a license to use Outlook for Desktop. I have no "personal" mail accounts such as Gmail etc. So I have, at this point 1x Outlook license.

* I have ONE Business Standard license for my work e-mail (which gives me Exchange Online and grants me ANOTHER license to use Outlook for Desktop, on the same PC). So at this point, I have "2x" Outlook licenses. One occupied by this e-mail address, one left.

* I have ONE Business Basic license for a another e-mail (which gives me Exchange Online but NO desktop apps). So, at this point, I SHOULD be able to add this account because I have 1x Outlook license still left. But I can't. I can no longer add a second "business" e-mail, because "it doesn't have a separate (in my case, therefore, 3rd) license for apps (i.e. Outlook)".

The takeaway is: You can no longer add a mail account in the new Outlook if said mail account doesn't come with its OWN Outlook (apps) license.

This is ridiculous beyond understanding. Unacceptable to the point that if they don't fix this, I'll cancel BOTH Exchange licenses and move over to Google Business with my domains. Based on THIS interpretation though, they should therefore BLOCK adding 3rd party mail services, as they don't come with Outlook licenses! I'll give it a few days and then decide.

So, let me get this straight.

* If I have a free @outlook.com email address I can totally add it to my Outlook for Windows app and use it in any way I need

BUT

* If I have a working email address covered by my Microsoft 365 license that I pay for, in this case, I CAN'T use Microsoft Windows Outlook to work with this email address.

Isn't it a kind of stupidity from Microsoft's side?

Hi,

I wanted to share my experience with this problem, I'm facing the same error as you guys when I try to add my work email.

After the MS event recently, I gave the new outlook (preview) another shot by switching it on, in the old Outlook app and I saw they updated the icon and fixed some features that were buggy before. But I still couldn't log in to my work account and got the error message.
By the way, I have the business basic plan and I noticed on the MS 365 website that the basic plan doesn't include desktop apps, only web version. So, I tried adding my school email which is "Business Standard", and which has the desktop apps included and it worked fine, no error at all.

So, I upgraded one of my business licenses from basic to standard and now I can add it to the new outlook desktop app. So, it seems like, if you are already logged in to the old or new outlook apps, DON'T log out or you won't be able to log back in unless you upgrade. I wish Microsoft would have told us this clearly or maybe I missed it.

They're all M365 Business basic. Okay, but then how I was able to login before? Did Microsoft make those changes now? I assure you that I had M365 Business basic all the time and I was able to login in this app, but now I can't.