Email: IP Warmup

To help inbox providers determine your sender reputation, it's important to “warm up” your email IP address and domain by gradually increasing sending volume for a minimum of 30 days. This builds your sender reputation and helps to prevent unexpected delivery failures.

Sending too many emails too quickly can cause inbox providers to throttle (temporarily defer acceptance) the mail, resulting in a high rate of delivery failures. 

Your sender reputation

As your email volume gradually increases, the inbox provider's machine learning algorithms will determine your sender reputation based on the following rates:

  • Bounce per sent
  • Delivered per sent (delivery rate)
  • Marked as spam
  • Unsubscribes per sent
  • Unique click
  • Unique open

The more conservatively you ramp up your daily volume, and the higher the delivery rate and user engagement, the better. Note that sender reputation is evaluated based on a 30-day rolling calendar.

To build a positive sending reputation during warmup:

  • Start by targeting engaged (0 to 6 month) subscribers with relevant content and expected mail (e.g. weekly newsletters and product updates) 
  • Expand target audience week by week based on audience engagement
  • Avoid including time sensitive promotional codes that could expire and cause recipients to complain
  • Avoid A/B testing during the warming period (in case you need to troubleshoot an issue)
  • Monitor your engagement metrics and adjust targeting or mailings as needed

Take a look at our Email best practices for more tips to improve and maintain delivery rates and sender reputation.

Warm-up schedule

Leanplum’s email service provider (ESP), SendGrid, recommends the following daily email schedule to warm up an IP address. Your Customer Success Manager can help you with this process, but if you prefer to do it yourself, be sure to follow this schedule when you start sending emails.

day Aggressive
1 100 50
2 1,000
3 10,000  1,000
4 50,000 5,000
5 100,000 10,000
6 400,000 100,000
7 1,000,000 400,000
8 2,500,000 600,000
10 5,000,000 1,000,000
11 7,500,000 1,600,000
12 10,000,000 2,000,000
13 12,500,000 3,000,000
14  15,000,000 4,500,000
15  20,000,000 7,000,000
16  30,000,000 9,000,000
17  50,000,000 12,000,000
18  80,000,000 15,000,000
19  100,000,000 18,000,000
20  150,000,000 22,000,000
21  200,000,000 27,000,000
22  300,000,000 40,000,000
23  400,000,000 55,000,000
24  500,000,000 65,000,000
25  600,000,000 75,000,000

Note: The “aggressive” schedule should be followed only if you are targeting your most engaged subscribers (those who are likely to open your email and create positive metrics).

Warming up your IP with random user buckets

Depending on your number of Daily Active Users, one way to limit your emails per day is to add User Buckets to your Target. Each user is randomly assigned a bucket between 0 and 999, making it easy to segment your target into smaller groups and gradually ramp up email sends.

  1. In the Users page, click Add Segment to open the dropdown, then select User Bucket.
  2. Enter a range of two numbers after "User bucket is between", or select a different operator by clicking on “is between.” For example, the target "User bucket is between 0 and 250" should include roughly one-quarter of your users (250/999).
  3. Hit the search button to see your results, which will include an estimate of the number of users in your segment. Adjust the User Bucket and target until the user estimate matches the recommended volume from the warm-up schedule.
    Tip: You may also want to add segment criteria for "User attribute email is set" AND "Unsubscribed from all marketing emails is false" to ensure that your user count only includes users who can receive emails. Save this segment to make it easy to use again later.
  4. Click "Send a message to matching users" to pre-load this target into the message composer, then select Email as your message type and customize your content.
  5. For the next email message (tomorrow), repeat these steps but choose a different range of buckets that includes the number of users recommended for the next day of the warm-up schedule.
    Note: User buckets are persistent, meaning that the users in each bucket will remain in their bucket throughout their experience with your app.
    So if you send buckets 1-5 an email, then send buckets 1-10 an email the next day, the users in buckets 1-5 will receive both emails. Keep this in mind when choosing user buckets, and try not to send the same group of users too many messages.

Note: If you have a very large user base, User Buckets may not be able to limit your email list to a small enough group when starting out. In that case, you can use other targeting techniques to limit the number of email recipients.

Targeting an engaged audience

The most important things when warming your IP are to 1) limit the size of the email list, and 2) ensure that engagement is high. Targeting highly engaged users with relevant content is the best way to ensure users will open your emails and improve delivery rates.

Some possible email target ideas include:

  • Targeting a set list of user IDs (of known users)
  • Targeting by last active (All Users > Lifecycle > Last Active) to find users who have been active recently

Other resources

Here are some other things to consider when starting out:

Was this article helpful?
Have more questions? Submit a request