Generally the reason of this error in misspelled or wrong address typed in address bar to connect exchange server. So firstly i would suggest you to check the URL which you are using to connect exchange and let me know the result.
1. I open outlook and then type / paste exchange server link (in my case: https://owa.compName.com/ews/exchange.asmx) in server field and then I get this error.
2. Then I change server field https://owa.compName.com/owa.
3. Now I quit outlook, quit form background running too & then again open outlook.
4. Nothing happened.
5. Then I send dummy email, it takes more than usual time to send.
6. But after that it works fine and I repeat this process when I start my laptop.
You can do one thing to resolve this error.
Outlook for Mac relies on Exchange Web Services (EWS), it does not support MAPI. Which is why you get this error.
So you can enable basic authentication of IIS (Internet Information Services) to access Exchange services for Mac.
To do this just go to IIS Manager in windows server and then expend default web site from left panel, if not expended. Then select EWS from left panel and select (double click) Authentication in IIS at Result panel which is at middle of window. Then in authentication just Enable Basic Authentication.