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

I was able to get around this error by signing into the old Outlook with my work account only, hitting the New Outlook toggle, signing into New Outlook with my personal Outlook.com account after encountering the error message for my work account, then removing my personal Outlook.com account. It caused the application to reload with my work account signed in.

I've heard many people say that "Microsoft is not listening." That is partially true. They're not listening to this particular thread - this is a community/peer-support forum. You can see that even the original responders have checked out.

The reviews might get some traction, but they only go to the coders who actually wrote this abomination.

However, Microsoft DOES listen to, and DOES respond to, the items in their feedback portal - especially those that get lots of attention.

We've created a master item in that portal to cover all of these issues. Could everyone in this thread please go here:

https://feedbackportal.microsoft.com/feedback/idea/2f7925cb-3a80-ee11-a81c-000d3ae46fcb  and both comment on, and especially UPVOTE this issue, so that it continues to gain traction and visibility within Microsoft?

And @dean03032 , although this isn't a fix, if you would consider accepting this as the "answer" to your thread, it will give more visibility, and point more people to the complaint in the feedback portal. The more upvotes we can get there, the faster we can get Microsoft's attention.

Thank you!

Alas the only fox that works right now is to upgrade your license. It sucks. But unless you fancy convincing MS otherwise, we’re just shouting into the void. I’ve had to upgrade from Business Basic to business Standard. Microsoft. You officially suck. If some clients didn’t insist on using Teams calls, I’d have run away and never paid you another penny.

I have the same issue - all of a sudden - as in late last night. prior to that it was working just fine, no issues. I'm on office 365 E1, which has always worked. What is the issue and how do I fix it, as I'm the sole admin on the account.

Apparently, I've found a solution of the problem. Actually not a real solution, just a tricky workaround.

I have Microsoft 365 Business Basic Plan and wanted to try New Outlook, but got the same error message as topic starter did. I wrote to Microsoft Support and quite quickly got the answer. They said:

"…please be informed, that the Microsoft 365 Business Basic plan provides access to the Web and mobile versions of Outlook. Unfortunately, the desktop version of Outlook for Windows is not included in this plan. To illustrate, I have attached a screenshot below for your reference."

Of course I wasn't satisfied with the answer because I'm not going to use Office 365 Desktop Applications, I only want to use FREE New Outlook application as a mail client to access my Exchange mailbox the same way like I do that with Mail & Calendar for Windows. I thoroughly explained my standpoint in reply to Microsoft Support and now waiting for their answer.

As a temporary workaround I bought Microsoft 365 Business Standard subscription for a month and (surprise!) I managed to add my Microsoft Business mailbox to New Outlook. After that I canceled new subscription and assigned back my old Microsoft Basic plan. Application works fine.

New Outlook checks subscription type only once before adding account and keeps that information in folder:

<username>\AppData\Local\Microsoft\Olk\EBWebView\Default\Local Storage\leveldb

After adding all accounts to New Outlook I saved a copy of that folder just in case. Even after reinstalling New Outlook it's enough to replace that folder and all accounts are restored.

It's a temporary solution but hope it could be helpful for someone too.