Question
Suppose you are attempting to create an autoresponder for an entire domain or selected users. Unfortunately, this feature is not yet supported.
Answer
If this is a feature you would like to see added to cPanel, you can vote for the following feature requests:
https://features.cpanel.net/topic/global-domain-autoresponder
https://features.cpanel.net/topic/autoresponder-generic-message-for-select-multiple-users
Workaround
Make use of the provided UAPI function "Email add_auto_responder" in a script or loop to add the autoresponder for each email account.