Why I cant add new email account in new outlook but in old it works?

Yes, I'm aware of that. As of today, all of my accounts, either exchange, or 365 work in every 3rd party client I've tried. That made my switch to MailBird a no brainer. As I said before, it checks all of the boxes, while MS just flops around like a fish on a boat deck. I just monitor this forum to see if MS ever fixes their litany of issues. Even if they do, I'd never go back. Just like I'll never go back to any MS internet browser. MS had their shot, and just watched as Google bowled them over with Chrome. Mailbird is 10 times the email client than Windows Mail ever was, with a simple intuitive interface to boot.

Had this issue. Found this post. Found a reply linking me to https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/outlook-on-the-web/enable-disable-employee-access-new-outlook#enable-or-disable-the-new-outlook-for-windows-for-an-individual-mailbox. I started testing with a handful of users. Initially, on Windows 11 I could not add an Exchange only account. I then ran the PS Command to check the value for the allowed access to the new Outlook. The users we tested were indeed set to no value. I set them to true, patiently waited for a few hours, then could add them to the machines needed. I believe they may have a bug in code or a typo in documentation, but it seems to me that -OneWinNativeOutlookEnabled has to be set to true and replicated through the O365 servers to appropriately work.

Everyone -

This was actually a conscious decision made by Microsoft. We're trying to get their attention to get this reversed.

My colleagues and I have created a master record for this issue, in the system that Microsoft actually looks at for complaints of this type. The record is here: https://feedbackportal.microsoft.com/feedback/idea/2f7925cb-3a80-ee11-a81c-000d3ae46fcb  . All of the issues surrounding this are document there, and we're gathering comments there as well. PLEASE consider taking a moment to visit that link, upvote that issue, and add your comments. This is the fastest and most correct way of getting this resolved. Thank you!

I fixed it myself. Just like I did with maps (google maps), Your Phone (google messages), Browser (google chrome), and now mail (mailbird), I just don't use the Microsoft solution. Each of those switches I have made came with no regrets. I appreciate your efforts, but my decision to switch also means I will no longer fight with Microsoft over their mail offerings. I've been battling with them over mail since 2015. Of all my mail complaints, the only on I know of that was addressed, was the ability to have HTML signatures in windows mail. Good luck, but I honestly believe you are wasting your time.