Internet Service Providers (ISPs) also value reputation, taking into account the behavior of an email sender when a message arrives. An email’s deliverability can depend on the trust and reputation of a specific IP address or domain. When branded with a poor sender reputation, emails can be marked as spam or altogether undeliverable, designating legitimate messages as low quality. In cases where an IP address has been flagged as disreputable, an act known as IP cooling can be used as a last resort to restore its credibility.
IP cooling—which is the process of letting an IP address sit for 30 to 45 days without activity—allows the IP address to establish a neutral reputation. Once at least 30 days have passed, your brand can begin gradually resurrecting that IP address for future sends through the process of IP warming, which allows senders to begin increasing the volume of outgoing messages to establish a positive reputation.
IP cooling isn’t a common occurrence—it’s only necessary when major reputation issues are preventing emails from being delivered. But for senders who may have practiced poor email list hygiene, IP cooling presents an opportunity to rebuild a good sender reputation by ensuring all email lists are squeaky clean and up-to-date.