ESPs warm up their ips and prepare them before putting them into production, where they're tasked with sending billions of emails on a regular basis. These IPs

ESPs warm up their ips and prepare them before putting them into production, where they're tasked with sending billions of emails on a regular basis. These IPs used in production are considered "professional grade". https://sendgrid.com/docs/Classroom/Deliver/Delivery_Introduction/warming_up_ips.html https://sendgrid.com/docs/Classroom/Deliver/Delivery_Introdu...