iCloud 
Send an automatic reply
If you won’t be answering your email for a while, you can set up an automatic reply. For example, you could send a message saying you’re on vacation and will reply when you return. (You can use this feature even if you forward your iCloud Mail to another email account.)
Send an automatic reply
In iCloud Mail, choose Preferences from the Action pop-up menu
in the sidebar.
Click Vacation.
Select “Automatically reply to messages when they are received,” then type the message you want to send.
Click Done.
Your auto-reply message is sent to an email address only once. Anyone who sends you multiple messages while you’re away receives your auto-reply only after the first message.
Stop sending an automatic reply
In iCloud Mail, choose Preferences from the Action pop-up menu
in the sidebar.
Click Vacation.
Deselect “Automatically reply to messages when they are received.”
Click Done.
Important: If your mailbox gets full, you won’t receive new email messages. If you’re going to be away from your email for a while, make sure you have space available for new messages.