As an email marketer, you’re most likely not a stranger to the term “IP warm up.” In this blog I’ll explain exactly what IP warm up is for those who are unfamiliar with the term, and I’ll explain exactly what it isn’t for those who are. Why do we warm up IPs? Unfortunately, the need to warm up IP addresses is mostly the result of a tremendous number of bad actors who abuse the medium of email to send recipients content and messages they didn’t agree to receive. The result of this is that inbox providers inherently (and necessarily) distrust unfamiliar senders. Because of this, IP warm up is necessary for anyone who wants their messages getting to the inbox. You are your IP address In the coming years, your sender domain will be just as important to your sender reputation as your IP address. However, as it stands today, the single most important part of your sender reputation is your IP address. To a large extent, your email traffic is “remembered” by inbox providers by which IP addresses the traffic came from. They remember which IPs they have seen good traffic from, which IPs they have seen bad traffic from, and they certainly recognize IPs they have never seen traffic from. This is where IP warm up comes into play. What it isn’t… I’ve read a number of articles and blog posts that suggest that warming up an IP for large volumes of email traffic is as simple as starting with a small number of messages and then increasing that number by some arbitrary value each day until you reach your desired sending volume. While this is certainly preferable to sending a blast of millions emails out of the blue on a few cold IP addresses, it completely misses the actual point of warming up IP addresses. What it is… As I mentioned earlier, inbox providers have been forced into a position where they must distrust any email stream they don’t recognize. When an inbox provider sees a large amount of mail coming from an IP address they do not recognize, they have to protect their users from this unrecognized mail stream by assuming it is untrustworthy and being more prone to blocking or filtering it. If you want to start sending email from a new (cold) IP address, sure, it’s a good idea to start with as little traffic as possible. However, if your messages are going unopened, they’re being marked as spam, or your list contains a large number of invalid email addresses, continuing to slowly increase your volume will do you no good. It just prolongs the inevitable. The inbox providers are going to realize your email is unwanted, and you’ll end up in the spam folder. If your first two sends generate low open rates, you should slow down and rethink your campaign strategy. If you see a high number of spam complaints, maybe you should rethink your subject lines, mailing frequency, or even the methods with which you collect email addresses. The takeaway Slowly increasing your sending volume will not, by itself, prevent long-term reputation damage. You have to be an active participant in the warm up process. Watch your logs. Pay close attention to how recipients are interacting with your mail, and make changes accordingly. A few extra days of gradual ramp up accompanied by steadfast monitoring and responsible list management can truly empower you to reach the inbox more consistently and avoid the revenue killing side effects of poor IP reputation. For more information on IP warm up, including same schedules, read our guide How to Warm Up an IP Address and if you’re interested in warming up your IP at SendGrid, check out our automatic IP warm up.