See the article - Interval hours of Cpanel Autoresponders – How it works?
Cpanel autoresponders:
Cpanel autoresponders are one time emails. Means if you receive an email from your web site visitor or a customer to a specific email address of yours, cpanel autoresponders send one time response to it.
Example of this:
* Vacation email where sender receives an email stating that you are on vacation.
* Email received by your customer stating that you have received the support request and would respond with in 24 hours.
Follow up Autoresponders:
On the other hand, the follow up Autoresponders differ from cpanel autoresponders by sending a series of messages to the subscriber.
Example of this:
* You set up an ecourse for 7 days with a 2 day interval. The autoresponder sends 7 messages for 21 days with 2 days interval in between each message.
* Following up your customer to upsell your other products by a series of messages with discount offers.
Cpanel autoresponders are integral part of the cpanel hosting software. You don't have much control over it. But your own follow up autoresponder is flexible enough for you to work with your email marketing campaigns.