From your cPanel, locate 'Autoresponders' or search for it from the search functionality at the top left hand of your cPanel.
You need to click on 'Add Auto Responder' button from this page to proceed further.
What the above field does is send a reply to the email address you receive the mail from auto responder after 2 hours interval. It won't send auto responder if you receive the second email within 2 hours period. If you want to send autoresponder every time you receive an email, simply put 0 in Interval.
You need to fill in a form next. A sample of the form fill-up is as given:
In the next 2 fields, enter the initial of your domain name for which you want to set autoresponder and add in your domain name.
For from and subject fields, you may leave what we have in place in the sample above or you can add your own subject. '%from%' sends the email to the address you received the mail from.
In the body, enter the message you want the autoresponder email to hold. Be sure to check 'This message contains HTM' if it does.
If you want you auto responder to start immediately and never to stop, let those fields be as they are else changed to 'Custom' and set your own period.