How do I set up an out-of-office reply for incoming emails?

To create an autoresponder, perform the following steps.

1. Log in to your Webmail interface at https://example.com:2096
2. Scroll to Autoresponder Options at the bottom of the interface.
3. Enter your name in the From text box.
4. Enter the subject that you wish the recipient to see in the Subject text box.
5. Choose the character set to send the email in from the options in the text box.
6. If you wish for the email to display HTML code in web form, select the HTML checkbox.
7. Provide a body for your message. For example, you might enter the following message: I am currently out of the office until July 2nd. You can reach me on my mobile phone for any emergencies.
8. Click Setup Autoresponder.

All email messages to your email account will receive this autoresponse until you remove it.

To remove the autoresponder, select Delete Autoresponder. 

Ref : https://documentation.cpanel.net/display/ALD/Mail+FAQ#MailFAQ-HowdoIsetupanout-of-officereplyforincomingemails?