This is part of a very good guide on IP warming made by the folks at SendGrid. You can find the link to download it directly from them below.
Whether you are just starting to send your first deployment or are increasing your email volume, there will come a time when you need to add a new IP address. As you know, an IP address is how the Internet Service Providers (ISPs) and other mailbox providers identify legitimate mail senders. Mailbox providers determine whether or not to deliver your mail to the inbox, spam, or junk folders based on your sending behavior and your IP’s reputation score. So, the better your sending practices, the higher your reputation score and the more likely you are to be delivered. Conversely, the lower your score, the more delivery failures you will experience (because low scores are indicators of poor sending practices).
A new IP address doesn’t have a reputation score since mail hasn’t been sent from it yet. So a new IP is considered “cold.” It needs to have mail sent through it in order to build its reputation. So how do you successfully get inboxed with a cold IP with zero reputation? The answer is…warm it up!
Getting Started with a New IP Address
FROM THE ISP PERSPECTIVE
Warming up an IP address means that you start sending low volumes of email on your dedicated IP and then systematically increase your email volume over a period of time. This gives ISPs the opportunity to recognize, identify, and evaluate your sending practices. During this period ISPs evaluate your sending behavior and con- tent to see how healthy your list is and how committed you are to deploying relevant information to responsive users. They even look at things like how many users opened your email, scrolled to the bottom, or moved your message to other folders.
The goal of warming up is to ramp up your sending volume to your anticipated “normal” levels, allowing the ISPs to gain trust in your sending behavior. You want the ISPs to learn your usual sending volumes so they can identify any suspicious behavior (i.e. spammers are known to inﬁltrate inboxes with malicious email by frequently switching IPs to circumvent ISP security checkpoints).
For example, both Hotmail and Yahoo! limit the daily sending allowance for all senders. They assess your reputation to determine your normal volume and then once that volume is exceeded, they block the “excess” email. However, as they get to know you, they will increase your daily limits. It’s all about establishing patterns and a circle of trust.
FROM THE SENDER PERSPECTIVE
This warm up period provides you with an opportunity to remedy any issues you may have prior to deploying to your entire database. With email delivery tools, you can determine if ISPs are throttling your mail and see
if your email is ending up in the inbox. Check your delivery rates by campaign, ISP, day, time, etc. and adjust accordingly.
Additionally, it’s a perfect time to reassess your content—identify which emails are generating the most (or least) response and ﬁnd out why. By dealing with a small sample, you can more easily identify patterns and then when your IP is warm, deploy the winning messages to your entire database.
As a sender, warming up your IP provides a very unique opportunity to monitor and optimize your entire email campaign. You’ll also ﬁnd that the good reputation you build during the warm up period will make your life much easier. Instead of chasing down problems, you can focus more closely on honing your acquisition strategy and working on product enhancements. Every delivered email increases your overall opportunity and teaches you more about your customers and their needs.
How to Warm Up Your IP
(Please note: The below is intended to be a suggestion only. Every sender is different and you will need email deliverability experts to help you determine the right warm up volume and frequency for your email program.)
HOW MUCH AND WHEN
As mentioned before, warming up an IP involves ramping up volume over a speciﬁed period of time. However what volume of email and over what period of time is different for all senders. How many emails you send depends on your own total email volume, but in any case you must send enough email at enough frequency so that your email reputation can be tracked. As a general baseline, you should send at least 50,000 emails per month at least twice per month (for 100,000 emails total) in order to need to warm up your IP. (This means that if your email volume is going to be really small but steady on a dedicated IP, you don’t need to worry about warming up—you’re off the hook!) Most reputation systems only store data for 30 days, so you should not go 30 days or more without sending on an IP. If you do, then you will need to warm it up again.
The biggest hurdle is knowing where to start. First, choose a segment of your email ﬁle to warm up. For instance, choose your welcome message as your trial segment for your new IP. Welcome messages do several good things; they serve as a permission reminder, they reiterate your value proposition, and they have calls to action to generate response. The point is to select a mail stream that has strong permission practices. This will help build your reputation and solidify your legitimacy as a sender in the eyes of the ISPs.
Once you’ve decided on a segment, determine the amount of email you should send. (See chart on Page 5 for sample calculations.) Once you determine your volume, send that same number of emails for several days in a row and then gradually increase your volume. This process can last up to 60 days. However the majority of SendGrid clients warm up their IPs within 30 days with some completing the process in as little as 1-2 weeks. To determine speed, use your results as a guide. If you are attaining good email deliverability with high engagement rates, then you can try to speed up the process. However, if you get throttled, tap the brakes and slow it down.
MAINTAIN WARM UP ACROSS ALL ISPs.
You must maintain a steady volume during the entire warm up period at EACH ISP. (i.e. Split up your warm up schedule so each ISP is receiving a comparable amount of mail each day—don’t warm up Gmail on Monday, Yahoo! on Tuesday, etc.—evenly disperse your mail to each ISP on each day of warm up.) If not, your sending activity looks sporadic and you won’t be able to build a solid reputation.
Sample Newsletter Schedule
Estimate your total monthly email volume and divide that number by 30. Then, spread your sending evenly over the ﬁrst 30 days, based on that calculation.
Example: if you will send 90,000 emails/ month, start off by sending 3,000 per day over the ﬁrst month.
Estimate your total monthly email volume and divide that number by 15 instead of 30. Then, spread your sending evenly over the ﬁrst 15 days, based on that calculation.
Example: if you will send 90,000 emails/ month, start off by sending 6,000 for the ﬁrst 15 days. If you experience throttling, slow down the pace.
Sample Transactional Email Schedule
If you are already sending a ton of email, and decide to move to an ESP for the ﬁrst time or switch to a new vendor, you should migrate your sending a little bit at a time.
One way to do this is to split your trafﬁc and move small portions of it to the new IP over time. If you are already maintaining multiple mail servers, you can move your servers over to your new IP one at a time.
Typically, the organic growth of your business will, by its nature, create an ideal ramp. Since transactional email is usually dependent on the number of users you have, the growth in your customer base will create a nice, comfortable growth curve in your email volume.
Maintaining a Good Reputation
ASKING THE RIGHT QUESTIONS
Reputation is the key to maximum email delivery. Therefore, when switching providers or moving from a shared IP to a dedicated IP, you must ensure that you have the tools to regularly monitor your email deliver- ability along with the expertise and help of a reputable email service provider. While we’ve provided sample schedules on Page 5, each sender is different and you will need email deliverability experts to help you de- termine the right volume and frequency to get your email messages delivered as soon as possible.
DOING THE RIGHT THING
It may be tempting to fast track your warm up process but as the old cliché goes, patience is a virtue. Recovering from a bad move can be more costly than taking the time to build a good reputation.
Download the full guide at SendGrid here: