Setting up Zimbra Email account as Exchange ActiveSync in Outlook for Mac Office365

1- Since Office365, the NEW Outlook for Mac does not support Exchange/ActiveSync anymore.
Prior to setting up a new account, you must revert to the Legacy Outlook client:
See: Switching back from New Outlook to "old" Outlook.

2- In Legacy Outlook:

• Click on the Tools > Accounts to display the list of accounts
• Click on + to add an account.
• Select Exchange
• Enter the email address and click on Continue.
• Enter the rest of the information.
• Click on Add Account.

Here is how the screen should look like if your email address is user@his.com: