Domain warmup is a critical phase for any brand migrating to Klaviyo or launching a new dedicated sending domain. The objective is to establish a positive reputation with Mail Box Providers (MBPs) like Google and Outlook by gradually increasing email volume while maintaining high engagement. In the Klaviyo ecosystem, this requires a delicate balance between automated flows and manual campaigns. Because these two message types behave differently in terms of volume and engagement, treating them the same during warmup can lead to deliverability issues.
Understanding the Roles of Flows and Campaigns
Automated flows, such as Welcome Series, Abandoned Cart, and Post-Purchase sequences, are triggered by specific customer actions. These messages typically see the highest engagement rates because they are timely and relevant. From a deliverability perspective, flows are your greatest asset during warmup. They generate consistent, positive signals like opens and clicks, which tell ISPs that your mail is wanted.
Campaigns, on the other hand, are one-to-many broadcasts sent to a specific list or segment at a scheduled time. While they drive the bulk of revenue for most e-commerce brands, they also carry higher risk during warmup. Large, sudden spikes in volume from a new domain are often flagged as suspicious behavior. The key to a successful Klaviyo warmup is leveraging the high engagement of flows to 'shield' the gradually increasing volume of your campaigns.
Prioritizing High-Engagement Flows
During the initial phase of domain warmup, your flows should do the heavy lifting. You want to focus on 'low-hanging fruit', messages that users are almost guaranteed to open.
- Welcome Series
- This is usually your highest performing flow. Ensure it is active from day one, but consider adding a filter to only send to subscribers who have joined in the last 30 days to keep the audience fresh.
- Abandoned Cart
- These are high-intent messages. Because the recipient was just on your site, the likelihood of a spam complaint is extremely low.
- Transactional Flows
- If you are sending order confirmations through Klaviyo, these should remain active as they have nearly 100% open rates, providing excellent reputation signals.
It is important to audit your flows before starting the warmup. Disable any re-engagement or 'win-back' flows targeting unengaged users, as these can generate bounces or complaints that damage a new domain's reputation.
Structuring Campaigns for Gradual Scaling
Campaigns require more manual oversight than flows during the warmup period. You cannot simply blast your entire list. Instead, you must use Klaviyo's segmentation tools to create 'Warmup Segments.'
Start by targeting your most engaged subscribers, those who have opened or clicked an email in the last 30 days. In the first week, limit your campaign volume to a few hundred or a few thousand recipients, depending on your total list size. Each week, you can expand the engagement criteria (e.g., moving from 30-day engaged to 60-day engaged) and increase the total volume.
If you notice a dip in open rates below 20%, you should pause the volume increases and stay at the current level until engagement stabilizes. Monitoring these shifts with a tool like SenderSignal helps identify if these dips are due to content issues or actual placement shifts into the spam folder.
The Mechanism of Volume Throttling
Klaviyo does not automatically throttle your volume based on ISP limits; it is the sender's responsibility to manage the schedule. When running campaigns alongside flows, you must account for the total daily volume.
If your flows generate 1,000 emails a day and you plan to send a campaign to 5,000 people, your total daily volume is 6,000. During the first few days of warmup, a 6,000-email spike might be too aggressive for a brand-new domain. You may need to split your campaign into smaller batches sent over two or three days to keep the daily total within a safe growth curve. This smoothing of volume prevents the 'spiky' sending patterns that trigger automated spam filters.
Checklist for a Balanced Warmup
To ensure your flows and campaigns work in harmony, follow this technical checklist:
- Audit all active flows
- Ensure only high-engagement triggers are live. Use flow filters to exclude anyone who hasn't interacted with the brand recently.
- Set up dedicated sending domain
- Before warming, ensure your DKIM, SPF, and DMARC records are correctly configured in Klaviyo.
- Create tiered engagement segments
- Build segments for 30, 60, and 90-day engaged users to use for campaign targeting.
- Monitor daily totals
- Add your projected campaign volume to your average daily flow volume to ensure you aren't doubling your total output overnight.
- Watch for 'Smart Send Time'
- Be cautious with Klaviyo's Smart Send Time during warmup, as it can sometimes concentrate volume in a way that creates unexpected peaks.
Handling Deliverability Setbacks
Even with a perfect plan, you may encounter obstacles. If you see a sudden increase in 'Dropped' emails or a spike in bounce rates, your flows and campaigns are likely being throttled by a specific provider like Yahoo or Gmail.
In this scenario, the first move is to reduce campaign volume significantly while keeping the high-performing flows running. The flows will continue to provide the positive engagement data needed to repair the reputation. Once the bounce rates normalize, you can begin increasing campaign volume again, but at a slower pace than before. Integrating SenderSignal into your workflow allows you to see these placement issues in real-time across different inbox providers, ensuring you aren't flying blind when reputation dips occur.
Transitioning to Business as Usual
A warmup is typically considered complete when you can send to your full engaged list (usually 90-day or 120-day engaged) without seeing a drop in performance or an increase in spam folder placement. At this point, the 'balance' shifts. You can rely more heavily on campaigns for revenue generation, but the health of your flows remains the foundation of your long-term deliverability.
Maintain a healthy ratio of automated, personalized content versus mass broadcasts. Even after warmup, a domain that only sends mass campaigns will eventually see a decline in reputation compared to one that maintains a robust ecosystem of triggered, high-value flows.