Warming Your Sending Infrastructure

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It's essential to warm your infrastructure any time you make updates to your DNS records, such as after setting up a dedicated sending domain, or whenever you move over to a new email service provider. This trains inbox providers to see you as a "good" sender and strengthens your sender reputation. The basic process is as follows:

  1. Turn on high engagement flows
  2. Migrate your engagement data over from your previous email service provider
  3. Begin sending campaigns to engaged segments
  4. Monitor your performance

In this guide, we will walk through each of these points in detail.

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, and you do not want lower-performing flows or campaigns to damage your sender reputation.

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

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. 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 general guide on migrating your data over to Klaviyo.

Begin Sending Campaigns to Engaged Segments

Once only your high engagement flows have been live for a week and you ensure that 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 one-off email sends that perform poorly and could damage your deliverability.

Moreover, 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 will be at risk of having your emails moved to spam by ISPs (like Google, Hotmail, etc.).

If you're just starting out with Klaviyo, leverage historic engagement data from your previous platforms to create these segments. If you have been using Klaviyo for a while, but are just now migrating over to a dedicated sending infrastructure, use your Klaviyo engagement data. After your first send, a rule of thumb is to aim for open rates of 20% or higher, unsubscribe rates less than 0.2%, and spam complaint rates less than 0.08%. Keep in mind that these specific numbers vary per sender.

Please note that 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 do not send to over 30,000 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.


Send to Warming Segments

30 Day Segment

For your first send, aim for open rates of above 30%. 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.


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 throttling or smart send time
    This allows you to send X amount of emails over the course of Y hours. For example, if you have 10,000 profiles in this segment, and want to send 1000 per hour, send to 10% of your segment instead of all at once, and break up sending over time.
  • Take random samples of the engaged segment
    Taking random samples of your segment will allow you to send your desired amount of campaigns despite the size of your segment.

You want to 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.

Having trouble building your engaged segment? Contact our Success Team with a link to the engaged segment you're building, the prior ESP you've migrated from, and the list in your account that subscribers are added to once they've opted in.

60 Day Segment

After a few days of sending to a 30 day engaged segment and consistently seeing high engagement, you can begin to broaden your audience to a 60 day engaged segment as long as this doesn’t bump you up to sending to far too many profiles. 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 instead.


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.


120 Day Segment

After sending to your 30-90 day engaged audiences for a few weeks, you can begin to 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.


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% or your segment includes too many individuals.


Monitor Your Performance

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

  • Review flow analytics: Check back periodically on your flow's open, unsubscribe, and spam complaint rates to gauge the engagement with these emails.
  • Monitor campaigns using the trends report: This report will show you changes over time in all the important email engagement metrics. In particular, keep an eye on the graph showing Marked as Spam and Hard Bounce rates, and make sure to look into campaigns that were responsible for any spiky behavior.

Learn more in our guide to monitoring your deliverability and email performance.

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