When migrating to Klaviyo or starting a new dedicated IP, the first 30 days are critical for your long-term deliverability. Inbox Service Providers (ISPs) like Gmail and Yahoo look for consistency and positive user signals when they see traffic from a new source. If you immediately blast your entire list, you risk high bounce rates and low engagement, which can lead to permanent reputation damage. The solution is to leverage Klaviyo's powerful segmentation engine to build a 'warmup ramp' composed only of your most engaged subscribers.
The Logic Behind Engagement-Based Warmup
Deliverability is essentially a credit score for your sending domain and IP address. When you start fresh, you have no credit. ISPs are naturally suspicious of high-volume senders they do not recognize. By targeting only those users who have recently interacted with your brand, you guarantee a high ratio of opens and clicks. These positive interactions act as 'votes' of confidence, telling ISPs that your emails are legitimate and desired.
Starting with your most active users allows you to scale volume slowly while maintaining a high engagement rate. This creates a buffer; if you encounter a deliverability issue, it is much easier to diagnose and fix when your baseline metrics are strong. Without these segments, a sudden spike in spam complaints or bounces from an unengaged list could cause your emails to be throttled or blocked entirely before you've even begun.
Step 1: Defining Your 'Core' Engagement Segment
Before sending your first warmup email, you must define what an engaged user looks like in your Klaviyo account. If you have historical data migrated from a previous ESP, ensure that 'Opened' and 'Clicked' events are properly mapped.
A standard 'engaged' segment for the first week of warmup should include:
- Someone who has opened an email in the last 30 days.
- Someone who has clicked an email in the last 30 days.
- Someone who has recently subscribed (in the last 14 days).
- (Optional) Someone who has placed an order in the last 30 days.
In Klaviyo, use 'OR' logic between these conditions to capture anyone meeting any of these criteria. Ensure you also exclude 'Suppressed' profiles and anyone who has unsubscribed to keep your bounce rates at an absolute minimum.
Step 2: Tiering Your Segments for Volume Growth
As your warmup progresses, you will eventually exhaust your 30-day engaged pool. To continue increasing your daily volume, you must create broader tiers. This allows for a controlled expansion of your reach without diluting your engagement metrics too quickly.
Tier 1: The Hyper-Engaged (Days 1-7)
This segment targets the 30-day openers and clickers. This is your safest group and should be used to establish your initial footprint. Your goal here is to achieve the highest possible open rates.
Tier 2: The Recently Active (Days 8-14)
Expand your segment to include users who have engaged in the last 60 days. At this stage, you are doubling your potential reach while still focusing on users with a high probability of interaction.
Tier 3: The Active Base (Days 15-30)
Expand to a 90-day engagement window. By now, ISPs have seen two weeks of consistent, high-quality traffic from your domain. If your open rates remain stable above 20%, you can begin introducing users who haven't engaged recently but are still within a reasonable 'active' window.
Step 3: Integrating Flow Traffic into the Warmup
Many senders forget that Klaviyo's automated flows, like Welcome Series and Abandoned Cart, contribute to your daily volume and reputation. Because flows are triggered by user action, they inherently have high engagement rates.
During your warmup, you should turn on your highest-performing flows first. The positive signals generated by a Welcome Series can help offset the risks associated with larger campaign sends. Always check that your flow volume is included in your total daily send calculations. If your warmup plan calls for 5,000 emails on Day 5, and your flows are already sending 2,000, you should only send 3,000 via manual campaigns.
Step 4: Monitoring Metrics and Adjusting the Ramp
A warmup is not a 'set it and forget it' process. You must monitor your performance after every single send. If you notice a sudden drop in open rates for Gmail users, or a spike in bounces from Microsoft accounts, you must pause the volume increase.
Key metrics to watch include:
- Open Rate
- Should ideally be 25% or higher during warmup.
- Bounce Rate
- Must stay below 0.5%.
- Spam Complaint Rate
- Must stay below 0.1%.
- Unsubscribe Rate
- Should be below 0.3%.
Using a tool like SenderSignal can provide a layer of visibility that Klaviyo’s dashboard cannot. By running periodic seed list tests, you can see if your warmup efforts are actually landing in the primary inbox or if you are being diverted to the spam folder, allowing you to pivot your strategy before the damage becomes permanent.
Handling Older or Unengaged Lists
If you have a large list of subscribers who haven't engaged in over 120 days, do not include them in your initial warmup. These records are the most likely to be spam traps or to result in hard bounces. Only once your warmup is complete and your reputation is 'High' (as verified by tools like Google Postmaster Tools) should you attempt to re-engage these users.
When you do eventually target them, do so in very small batches, no more than 5-10% of your total daily volume. This prevents a sudden 'reputation shock' that could undo weeks of careful warming. If a user does not engage after a final re-engagement campaign, they should be sunsetted immediately to protect your long-term deliverability.
Why Consistency is Essential
ISPs look for patterns. If you send 10,000 emails on Monday, 0 on Tuesday, and 50,000 on Wednesday, you appear erratic and suspicious. The goal of using Klaviyo segments is to create a smooth, upward-sloping line of volume.
If you miss a day of sending, do not try to 'make up for it' by doubling the volume the next day. Simply pick up where you left off. Maintaining a consistent cadence with highly engaged segments is the fastest way to earn trust with mailbox providers. Using SenderSignal to monitor your domain health throughout this process ensures that you are moving at a safe pace and that your engagement segments are doing their job of securing your spot in the inbox.