The Mail app for macOS doesn't offer automatic or out of office reply options for email accounts. However, if you use an iCloud email address, you can set up automatic replies through the iCloud website. Then the email sender will know when you are absent and when you return. Below are instructions for setting up out of office replies in iCloud Mail.
Instructions for creating an out-of-office reply email in iCloud Mail
Step 1:
You access the icloud.com website and log in with your Apple ID account.
Step 2:
Switch to the new interface, users Tap the Mail app to adjust.
Step 3:
In the iCloud Mail application interface, click cog icon at the top of the Mailbox side column, then click Settings to adjust.
This time you Click on Auto-ReplyTo adjust automatic reply mode for iCloud Mail. Next, look at the content next to it Check Automatically reply to messages when they are received to set up out of office replies on iCloud Mail. We choose the time to use the out-of-office reply email according to the time frame.
You can enter your absent reply into the box below to save it.