How to ramp and warm your sending infrastructure

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You will learn

Learn how to choose the right process to warm your right Klaviyo sending infrastructure and help ensure you reach your subscribers. Warming your sending infrastructure is essential for all new Klaviyo customers, and for existing customers who are using new domains or infrastructure. All warming processes train inbox providers to see you as a "good" sender and strengthen or ensure your sender reputation.

In this guide, we will walk through each step in the warming process as it relates to your particular use case.

How to choose your warming process (if applicable)

Depending on what type of Klaviyo customer you are, if you have engagement event data, are using a new domain, and other considerations, your warming process may differ. Use the guidance below to decide which process you should follow.

Note that all use cases below are for accounts on shared IP’s. 

Use case and warming process to follow

New customers or using new domains

  • Follow the standard guided warming process below, if you are a new Klaviyo customer (either on a shared or dedicated domain) and:
    • have engagement data (i.e., opens, clicks, etc.) OR
    • are using a Klaviyo-built integration that syncs open and click events
  • You should also follow the standard guided warming process if you are using a newly registered domain (i.e., that is a domain created within the last 30 days).

Existing customers moving to a dedicated sending domain

  • If you are an existing Klaviyo customer moving to a dedicated sending domain, you do not have to warm your infrastructure again, as long as you have:
    • a domain that has been registered for at least 30 days AND
    • you’ve sent an email from Klaviyo already

Klaviyo customer without engagement events or data
You should use the platform warming process, if you:

  • do not fit into any of the use cases above OR
  • are not using a Klaviyo-built integration that syncs open and click events OR
  • simply do not any engagement data that you are bringing over to Klaviyo (e.g., you only have date-based properties such as “last opened,” “last clicked,” etc.).

Standard guided warming process

If you fall into the category of our standard guided warming process, you may see notifications appear in your account as you ramp up with Klaviyo or once you meet the qualifications for warming (see below). During guided warming, a banner will appear in your campaign editor instructing you on best practices based on the stage of warming you are in.

To see guided warming notifications you must meet the following qualifications:

  • Are a new account or an account that recently moved to a dedicated infrastructure
  • Have at least 5,000 active profiles
  • Have engagement event data synced to Klaviyo; for new customers. This can be synced from a previous ESP using one of our pre-built integrations

If you do not initially qualify for full guided warming, you may still see notifications from Klaviyo prompting action for optimal success as you warm your account. For more information on guided warming, head to our article About guided warming.

Note that if you have qualified for warming but did not send an email in the last 45 days, you will see the warming notifications dismissed. If you wish to warm your account (which we strongly advise), follow the directions.

1. Turn on high engagement flow emails

Three types of flows that typically see very high engagement include:

  1. Welcome series

  2. Abandoned cart

  3. Browse abandonment

We recommend turning these live the first day you begin using your dedicated sending domain and running them for 3-7 days before sending campaigns, depending on your sending volume of flows alone.

If you normally send winback or re-engagement flows, turn these off during the first couple weeks of warm-up. Also, refrain from sending campaigns larger than 10,000 recipients in the first week. It is crucial that you maintain high engagement, as you do not want lower-performing flows or campaigns to damage your sender reputation.

After your first week of high engagement with these flows, begin sending campaigns. Make sure to monitor deliverability and maintain high engagement with engaged segments and sending schedules.

2. Migrate historic engagement data
If you are warming your infrastructure due to moving to Klaviyo from another email service provider (ESP), it's important to take historic engagement data into account so that you accurately build engaged segments. This will allow you to more easily set up your sending infrastructure, as you can contact those that are already engaged with your brand, while limiting contact with those that may not want to hear from you. Klaviyo has guides to migrating your data over from a number of different ESPs to facilitate the import of engagement criteria, including:

If you are using an ESP that is not listed above, utilize our platform guidelines below to warm. 

3. Begin sending campaigns to engaged segments
Once only your high engagement flows have been live for a week and you have accurate engagement data in your account, you can begin periodically sending campaigns to engaged segments. Remember that your new sending domain is a clean start, so initial sends greatly impact your reputation. Sending to highly engaged segments over time helps to prevent any single low-performing message from damaging your deliverability.

With the release of iOS15, macOS Monterey, iPadOS 15, and WatchOS 8, Apple Mail Privacy Protection (MPP) changed the way that we receive open rate data on your emails by prefetching our tracking pixel. With this change, it’s important to understand that open rates will be inflated.

If your campaign analytics show a large number of iOS openers, we suggest identifying these affected opens in your individual subscriber segments.

For complete information on MPP opens, visit our iOS 15: How to Prepare for Apple’s Changes guide.

Create warming segments based on engagement over 30, 60, 90, 120, and 180 days. You will use these when sending over time, starting with your 30 day segment. If you send to inactive subscribers, you risk having your emails moved to spam by ESPs (like Google, Hotmail, etc.).

If you're just starting out with Klaviyo or migrating from another platform, leverage historic engagement data from your previous platforms to create these segments. 

However, if you attempt to send a campaign to more than the recommended amount of recipients during warming, Klaviyo will alert you with a warning, encouraging you to review this guide and lower the recipient count of your campaign. For your first campaign, we recommend that you send to fewer than 10,000 recipients. This recommended recipient count will then grow dynamically as you send to more people over time, so the warning will adjust accordingly, as shown below.

View of the Klaviyo Campaign Wizard, halfway with an alert in yellow if you exceed the recipient list size during your sender warming period

4. Send to warming segments
As you start to engage your 30, 60, 90, 120, and 180 day segments, you will want to aim for the open rates listed in each section below. However, it’s important to note that open rates may vary per sender and industry, so your focus should be following the guidance below along with attaining as high as possible engagement for your specific business. Learn more in our resource on monitoring deliverability performance.

30 day segment

For your first send, aim for open rates of above 30% if possible. Getting an open rate this high will require sending to a segment of anyone who has opened or clicked in the last 30 days, or those who subscribed within the last 15 days.

Klaviyo Segment page, setup to find subscribers who have or have not opened email in last 30 days or are not in the sending list in last 15 days

If your 30 day engagement segment results in a very large group of profiles, consider the following:

  • Tighten the criteria of your segment
    For example, tightening a 30 day engaged segment to 14 day engagement will shrink the segment size.
  • Use smart send time to divide up sends
    By using Smart Send Time, your email sends will be automatically divided up and sent over the course of 24 hours. This will help you send to smaller groupings of subscribers and continue to warm your IP. Additionally, you will learn the best time of day to send to these subscribers in the future. (Note that Smart Send Time requires at least 12,000 subscribers in Klaviyo).
  • Use batch sending to divide up sends
    Use batch sending to break up your email sends into smaller groupings of users.
  • Take random samples of the engaged segment
    Taking a random sample of your segment will allow you to break larger sends into smaller groups.

Be conservative in your sending during this time and strive for as high of engagement as possible. For subsequent sends, and as long as you're getting open rates above 20%, you can create a similar segment and relax the engagement criteria to 60 or 90 days. Continue with this strategy for a couple of weeks, and then further relax your engagement criteria to 120 or 180 days.

60 day segment
After a few days of sending to a 30 day engaged segment and consistently seeing high engagement, you can broaden your audience to a 60 day engaged segment as long as this doesn’t substantially increase the size of your sending list. Remember to stay conservative in the number of email sends during this time. Make sure your open rates stay above 20%. If they do not, return to your 30 day segment.

Klaviyo Segment page to find subscribers who have either opened or not opened an email in last 60 days or are not in the email list in last 30 days

90 day segment
If you feel as though you can continue to broaden past 60 days, create a 90 day engaged segment instead. Again, make sure open rates are 20% or higher, and if not, then tighten your timeline.

Klaviyo platform Segment page to find engaged and unengaged subscribers for email for past 90 days or are not in the email list in last 45 days

120 day segment
After sending to your 30-90 day engaged audiences for a few weeks, relax your engagement criteria to 120 or 180 days. Again, strive for high open rates above 20% and send to this limited group of profiles. The 120 engaged segment is shown below.

Klaviyo platform Segment page, displaying the setup to find subscribers who have or have not opened email in last 120 days or are not in the sending list in last 60 days

180 day segment
If you feel 120 days is too restrictive and want to expand to a 180 day segment, it will look like the one shown below. Tighten to 120 days or lower if engagement falls below 20%.

Display of Klaviyo platform Segment page, setup to find subscribers who have or have not opened email in last 180 days or are not in the sending list in last 90 days

5. Monitor your performance
These tools will help you monitor your performance as you warm your sending domain:

Platform warming process

If you cannot use standard guided warming (e.g., only have date-based data properties like “last open” or “last click”), you can use a modified version of guided warming. By following this modified platform warming, we are able to gather information to assign you to the right sending group and in parallel you are able to solidify your sender reputation.

Platform warming starts out with smaller, engaged audiences allowing you to gradually open up volume over the course of about 30 days. The information below provides a guide on how many emails you should send per day, to what volume, and the suggested data to use.

Day Subscriber volume (max.) Engagement to use
1 2,000 Clicks from the last 30 days
2 4,000 Clicks from the last 30 days
3 8,000 Clicks from the last 30 days
4 14,000 Clicks and opens from the last 30 days
5 21,000 Clicks and opens from the last 30 days
6 31,500 Clicks and opens from the last 30 days
7 47,250 Clicks and opens from the last 30 days
8 63,750 Clicks and opens from the last 30 days
9 86,000 Clicks and opens from the last 30 days
10 116,000 Clicks and opens from the last 30 days
11 150,000 Clicks and opens from the last 60 days
12 200,000 Clicks and opens from the last 60 days
13 260,000 Clicks and opens from the last 60 days
14 338,000 Clicks and opens from the last 60 days
15 440,000 Clicks and opens from the last 60 days
16 572,000 Clicks and opens from the last 90 days
17 744,000 Clicks and opens from the last 90 days
18 967,000 Clicks and opens from the last 90 days
19 1,255,000 Clicks and opens from the last 90 days
20 1,631,500 Clicks and opens from the last 90 days


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