IP address warm-up refers to the process of gradually increasing the sending volume of emails from a new or inactive IP address in order to establish a positive reputation with internet service providers (ISPs). This is done to ensure that emails are delivered to the intended recipients’ inboxes instead of being marked as spam. The warm-up period typically involves sending a small number of emails and gradually increasing the volume over a period of time, allowing ISPs to monitor and assess the sender’s reputation. This practice is crucial for businesses and organizations that rely on email marketing as it helps to maintain a good sender reputation and improve email deliverability.