Exchange + O365 not working on Mac

Dear All,

I have a weird issue. I have two e-mail accounts: (1) Exchange with domain+user as user name; (2) regular O365 account.
I also have two computers a Windows desktop and a Macbook.
On the Windows machine everything works fine, both accounts work together like a charm.
On the Macbook if I install the Exchange account, it works perfectly fine. If then I install the O365 account, the Exchange account stops working. If I then remove the O365 account, restart eMClient, Exchange account starts working again.
The O365 account itself works perfectly fine. If I add the O365 account first, and then add the Exchange, same thing happens.
Tried it on another Mac (Intel and M1 both), same thing. Tried on Big Sur and Monterey, same deal.

Please advise, what could be the solution.

Thank you!