📧 What the heck is IP Warming?
Learn how to warm your IP effectively and efficiently
Hey there, it’s Jacob at Retention.Blog 👋
I got tired of reading high-level strategy articles, so I started writing actionable advice I would want to read.
Every Tuesday I share practical learnings you can apply to your business.
What is IP warming and why should you care?
IP warming builds a positive sender reputation for a new IP address in the eyes of mailbox providers
Your sender reputation is one of the largest factors in whether your email is delivered to the inbox or not.
ℹ️ IP reputation != Domain Reputation. Your domain reputation is attached to your sending domain (or subdomain) and is separate from your IP address reputation. Sendgrid has a good article explaining the difference here.
Who needs to warm IPs?
If you’re implementing a new ESP
If your email volume has increased and you need to add an IP address
If you’re changing email service providers and need to also change IPs
If you’re changing sending domains (but less critical if you have the same IPs)
If something has gone wrong and you’ve experienced some major drop in your reputation
…you should warm your IP.
ℹ️ You don’t need to warm your IP address if you have a shared IP from your email service provider. This IP is already sending emails for other domains so it’s “warm.”
What happens when you don’t warm your IP in the above scenarios?
Your emails won’t reach your customers or users
Your sender reputation will plummet
You’ll waste way more time trying to fix the issue than if you had been more careful upfront
You’ll lose money by not being able to retain or sell to your customers effectively with email
Don’t start IP warming until you have your SPF and DKIM records set up. You should also get DMARC set up at some point, but it’s not a blocker to start sending.
And don’t send to people unless they’ve opted-in to receiving emails from you!!
How do you do it?
The goal is to increase your email volume gradually until you reach your “normal” sending volume.
Spammers have large spikes in email volume and frequent changes in IP address, so warming allows mailbox providers to learn your sending behavior to make sure you’re not spam.
What’s a typical IP warming schedule?
Start by figuring out your normal email volume per month
For example, if you’re sending 2MM emails per month you want to slowly ramp up to an average of 65k/day
Start with 50 emails per day and gradually increase volume each day over 2-3 weeks until you reach the desired volume
Day 1: 200, Day 2: 400, Day 3: 800, Day 4: 2,000, Day 5: 2,000, Day 6: 4,000, Day 7: 4,000, Day 8: 8,000, Day 9: 8,000, Day 10: 15,000, Day 11: 30k and so on
I know starting that small may sound silly, but if you have a completely new domain and IP this is the best path.
If you have a larger send volume, you’ll need to scale a bit more aggressively so it doesn’t take forever
Other schedules recommend doubling volume for the first week (250, 500, 1000, 2000, 4000, 8000, etc), and then increasing by 20-50k each day in your 2nd week, and then by 100-200k each day in your 3rd week.
Closely monitor your reputation, deliverability, and inbox placement. If anything is dipping, pause on increasing volume until deliverability stats improve.
Who do you send to and what do you send?
Your first 2 weeks of recipients should be loyal and active user segments to get the highest engagement metrics
Specific emails that have historically high engagement rights (opens, clicks) should be used for IP warming.
By pairing a loyal and active user segment with an engaging email, IP warming can be achieved much faster with a higher reputation
Welcome emails have very good engagement rates
Email signup verification emails can also be good because they usually force the user to open and click the email if they want to register their account.
How do you measure your reputation and technical setup?
Useful for checking the reputation of an IP address or a domain
Allows for insight into Spam Rate, IP Reputation, Domain Reputation, Feedback Loop, Authentication Rate, Encryption Status, and Delivery Errors for all emails sent to Gmail.
An easy way to check your SPF, DKIM, DMARC, and other header info is by sending a test email to your Gmail account, and clicking “Show Original” in the dropdown arrow in the upper right corner after you open the email.
Tests “spammy-ness” of your emails and offers steps to improve your email and sender reputation
An industry standard. Multiple tools for checking blacklist status, authentication status, and overall IP or domain health.
Barracuda maintains a block list and will tell you if your IP/domain is on it, and/or if your reputation is poor. There isn’t a ton of detail in the reports, but helpful nonetheless.
💡 Want a deeper dive into deliverability, domains, sub-domains, and inbox placement tools?
Listen to this Humans of Martech Podcast with Mailgun’s VP of Deliverability.
Check your reputation and deliverability metrics using the above tools every day while warming
Maintain a spreadsheet and record your scores every day to easily notice decreases
If you notice decreased performance, maintain the previous day’s volume until the metrics improve.
If that doesn’t help, try to segment open and click rates by email domain and adjust your target audiences to more engaged recipients for that domain
Typically, when starting warming, some of your email will not be delivered immediately and may be held by the mail client for a day or two (called “bulking”).
After your first sends, you can watch your sent/delivered ratio increase over time.
The first time I warmed an IP I was very worried because it looked like half of my email wasn’t being delivered but by the next day, the majority had been delivered.
Take it slow and have patience and you’ll have success.
A couple of last helpful tips:
Bulking at Yahoo, AOL, and Gmail will slow after some sends with solid positive metrics, but it can take time. Keep sending to engaged users.
Delays at AOL, Microsoft, and Comcast are normal and will decrease as your reputation builds.
If a large percentage of your emails aren’t being delivered, decrease volumes overall, or only for that mailbox provider, and send to more engaged users
Potentially, blocking by a certain mailbox provider can occur if your recipients aren’t engaged enough. Segment to a more engaged audience, and keep sending.
Carefully monitor your Reputation during IP warming process. Metrics mailbox providers care about:
Hard bounce rate – Aim for less than a 0.5% bounce rate while you are warming your IP.
Spam complaints – Ideally, you only send to recipients who have opted-in. But sometimes it’s easier to hit SPAM than it is to find the opt-out link. ISPs are looking for less than a 0.1% spam rate.
Open Rate – Having an open rate that is consistent and growing will dramatically improve your reputation and can reduce the amount of time it takes to warm your IP.
This is harder to measure accurately with Apple’s Mail Privacy Protection (MPP) as they’ll trigger an “open” for any email delivered to an Apple mail client. Email rates should still be monitored, but all the information should be taken with a grain of salt. We’ve seen email rates double for some brands after MPP was released.
Email Clicks - Email clicks are even more important for your brand after MPP. This is one of the only positive engagement metrics that you can accurately track, so place more emphasis on this metric when warming a new domain and/or IP
Unsubscribe rate – Having recipients unsubscribe from an email is not necessarily a bad sign for IP warming. The ISPs still see this as an interaction with the email. It’s not as good as an open or a click, but much better than a spam/abuse complaint.
If you’re still struggling with your deliverability or inbox placement, join the Email Geeks Slack community and go to the #deliverability channel. Some of the most capable email deliverability experts will help you there.
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