Do I need an IP warm-up when moving to a new ESP with shared IPs?

Despite moving to a new ESP with shared IPs, a consistent theme across various sources indicates the importance of an IP warm-up process. Although shared IPs possess an existing reputation, new senders still need to gradually increase their sending volume. This allows mailbox providers like Gmail to learn the sender's patterns and prevents the triggering of spam filters. Furthermore, a sender's reputation should be consistently monitored to ensure adherence to email marketing guidelines. Factors such as sending habits, frequency, and engagement rates contribute to the overall reputation of the shared IP. Sending a large newsletter immediately after the transition is discouraged. It's best practice to transfer suppression lists and engagement data from the prior ESP and treat the first few weeks as a soft warm-up period. While ESPs handle some aspects of IP reputation, a sender's behavior and sending practices are still crucial for maintaining deliverability.

While moving to a new ESP with shared IPs might seem like it negates the need for IP warming, the consensus is that a warm-up period is still crucial for optimal email deliverability. Even on shared IPs, mailbox providers like Gmail analyze sending patterns to assess sender reputation. A sudden spike in email volume from a new IP, even a shared one, can trigger spam filters. Therefore, gradually increasing sending volume, starting with highly engaged segments, is recommended. Testing deliverability, monitoring sender reputation, and bringing over suppression lists from the previous ESP are also essential steps. ESPs are only partially responsible, so taking the correct steps can prevent deliverability issues.

Even when moving to a new ESP with shared IPs, experts recommend warming up the IP address. While the ESP manages the overall reputation of the shared IPs, senders still contribute to it through their sending habits, frequency, and engagement rates. Warming the IP gives machine learning filters time to learn the domain is legitimately sending from those IPs. A sudden increase in email volume without warming can negatively impact the IP's reputation and cause deliverability problems.

Even with shared IPs, documentation from various providers like SparkPost, Google Postmaster Tools, Microsoft, and AWS recommends a gradual IP warm-up. While shared IPs have an established reputation, new senders must gradually increase sending volume to help mailbox providers learn their sending patterns and prevent triggering spam filters. It's also crucial to monitor sender reputation and ensure sending practices align with guidelines, as a sudden change in patterns can still negatively impact deliverability.