Email: IP Warmup

When starting out, it's critical that you "warm up" your new email IP address by gradually increasing your daily email sends. Sending too many emails too quickly can get you labelled as a spammer and - in extreme cases - get your IP suspended or blocked.

Email providers are very aggressive when it comes to spam filtering, and the first month or two using Leanplum for email are critical for building your "sender reputation."

Your Sender Reputation

Your sender reputation is based on multiple factors, including:

  • Spam complaints
  • Mailing to Unknown Users (bounces/undeliverables)
  • Mailing to Spam traps (addresses setup by ISPs to catch spammers)
  • Email volume (sending a lot of email too quickly)

The more conservative you ramp up your daily volume, and the higher the delivery rate and user engagement, the better. 

Best Practices

  • Only send emails to known users
  • Follow the warm-up schedule (see below)
  • After warm-up, maintain a consistent schedule of emails (don’t let your IP go dormant, otherwise you’ll have to warm it up again).

Warm-up Schedule

Sendgrid recommends the following daily email schedule to "warm-up" an IP address. This is something that your Customer Success Manager can help you with, but if you prefer to do it yourself, be sure to follow this schedule when starting out.

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

Only follow the “aggressive” schedule if you are very confident in your email lists and that those users will engage with the email (open, click). Any undelivered or unopened emails will count against your sender reputation, and that can’t be undone. This is why we recommend a conservative approach when warming up your IP address.

Warming up your IP

Depending on your number of Daily Active Users, one way to warm up your IP is to use User Buckets. Because each user is randomly assigned a bucket between 0 and 999, this can be an easy way to randomly segment your total users, and quickly ramp up your email sends.

  1. For the email message, add a new target. Select User Buckets
  2. Enter a range of two numbers, or select a different operator by clicking on “is between”
  3. You'll see a user count appear above the Targets section. Adjust the User Buckets, or targets, until this number matches the recommended volume from the warm-up schedule.
  4. Select “Immediate” delivery (to ensure the emails go out today)
  5. For the next email message tomorrow, repeat these steps but choose a larger range of buckets (to increase the number of sends for that day)

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

There is a bit of artistry required here because you need to 1) limit the size of the email list, and 2) ensure that engagement is high. Using targeting metrics to find highly engaged users may be the best way to go to find highly engaged users.

Some possible targets early on are:

  • A list of user ids (of known users)
  • Targeting by last active (Lifecycle > Last Active) to find users that have been active recently

Other resources

Here are some other things to consider when starting out.

10 Tips to keep email out of the spam filter
CAN-SPAM Act Compliance Guide for Businesses

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