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

People, you are wasting your time.

Microsoft have you by the short and curlys and they know it.

Subscription price of business basic went from £3.80 (GBP) to £4.50 then to £4.90. now they are forcing 12 month contract unless you pay another 20% making it £5.88. same percentage increases on other packages. If you are a partner (reseller, even just a small indirect reseller) then they come after you if your client goes bump. The partner is on the hook for paying out the rest of the contract.

At the same time, they are forcing you to have licenses that you don't want, as in this very discussion here, and also in the case of office apps (word/excel) being signed-in to a secondary account that has business basic - accessing files on OneDrive for example. They are forcing you to pay for the full license for every single account even if all on the same computer and the same person, and at these massively inflated prices.

And the problem is.. there is no negotiation. You have no voice at all. It's take it or leave it. Google aren't any better really.

It's time to ditch them altogether. Go back to basics. IMAP mail or SoGo or something, libre office, back up your data with Kopia and Backblaze instead of OneDrive. Just say NO.

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.

I finally got my reply from MS support.

"Thank you for your patience. Upon analyzing the error message and the license that has been assigned to your mailbox, we would like to inform you that you are facing this issue due to the license your company choose to purchase. New Outlook will not support the E1 license by design. We understand that this account will not support in new Outlook however you can use the same on OWA [Outlook web app]."

Utterly bonkers. I can use my free emails like Google and Apple, but they deny me using my paid for Business Basic MS email? I can only assume whoever made that decision was on mind altering drugs, or that they have decided to quietly sunset Outlook, despite spending a fortune to update it. Do they really think we are going to think "oh, the thing that we used to get as a part of that subscription is no longer allowed, here have some more money Microsoft so we can do something with you that we can do for free somewhere else?" I suspect we are about to see a boom time for the growth of 3rd party outlook alternatives. Good. I'm not walking away from outlook. I'm running.

Hopefully someone from Microsoft is taking a look at this issue. Just to go on record. Outlook works great with my personal account. The second account that fails is a fully licensed Outlook account. So having a "legitimate license" is not the issue. We own and pay for both license. Thank you for putting some resources behind this and getting it fixed.

Something's weird going on. I logged out from the new Outlook app and when I try to login, now I get the same error and can't sign in. I don't understand why, because I logged in before and was using it all the time.

I'm one of the admins there. I checked the subscription. That's what it shows me.