How to Fix: To check if you have entered the correct information about the account, try to access the account from OWA or other Exchange applications.
How to Fix: Outlook for Mac 2016 is compatible with Exchange accounts of Office 365 for Business, Exchange Server 2010 (Service Pack 2) or its lower versions.
Tip: Users can go to Control Panel and check the “User Information” to confirm server name. Make sure you do not check the option of “Configure automatically.” Then add webmail server name.
Then choose “User Name and Password” as the ‘Authentication Method.’ Again, enter your Username and password of Exchange account for the purpose of authentication. On the next screen, you will be asked to provide your Exchange account information.On the Accounts screen, choose Exchange or Office 365 to configure Mac Outlook into Exchange Server.There will be two options on the next screen.Click on the arrow and then on Get Started button on the next screen to start the procedure of Exchange configuration. In case you are opening this Outlook account for the first time, you will have an arrow sign > on the Welcome screen of Outlook.In case a pop-up appears to ask permission about to use information in a keychain, click on Always Allow button.Open your Mac machine and click on Applications in ‘Finder.’ Then you have to double-click on Microsoft Outlook to launch it.Users have to follow these steps to set up their Outlook for Mac account to Exchange.
How to Configure Mac Outlook to Exchange Server