Mac – Office for Mac 2016, the Outlook can’t connect with the company Exchange Server

Outlook 2011 requires an Exchange 2007 and above server. This is because Outlook 2011 works over the Exchange Web Services protocol (EWS). This wasn't Apple's decision, but Microsoft, as it is the latest form of the Exchange service as they are phasing out MAPI, the legacy Exchange protocol. Apple's Exchange implementation in 10.6 and 10.7 also uses EWS.

iOS devices however connect to Exchange via ActiveSync, which is supported all the way back to Exchange 2003. ActiveSync is designed for mobile devices and does not work on a desktop system.

First, make sure that you're up-to-date with your Outlook updates. The most recent version of Outlook is 14.3.2.

One relatively easy option would be to remove your Exchange account from Outlook, quit Outlook, quit the Database Daemon, and then launch Outlook and re-add your Exchange account. Another option would be to create a new user account on your Mac and add your Exchange account to Outlook there. In either case, this will tell you whether this is an issue with something on Exchange or if it's local to Outlook.

There are additional troubleshooting steps available in this Outlook:Mac KB article, but the steps above are where I would start because they're the easiest.