Automatic replies in Outlook for Mac

Click Tools in the Mac toolbar and click Automatic Replies.​​​​​​​​​​​​​​

In the Automatic Replies window, turn the Send Automatic Replies toggle on.​​​​​​​

You can then type in your message you want to reply to emails as well as how long you want the automatic applies to continue.

You can also have separate replies for people outside your organization if you're using a company or organization email account.

To turn off automatic replies, just turn the Send Automatic Replies toggle off.