Warming up a sending domain in Klaviyo is a critical technical requirement for any ecommerce brand migrating platforms or launching a new domain. When you send from a dedicated domain, you are establishing a unique reputation with Mailbox Providers (MBPs) like Gmail, Outlook, and iCloud. Without a historical record of positive engagement, these providers may view large-scale sends as a security risk or spam.
The goal of a warmup is to demonstrate that you are a legitimate sender by gradually increasing volume while maintaining high engagement rates. This process allows MBPs to observe your sending patterns, verify your authentication protocols, and monitor how their users interact with your content. Successful warmup ensures that when you reach your peak seasonal volume, your emails land in the primary inbox rather than the promotions or spam folders.
Technical Prerequisites Before Starting
Before sending your first email, your infrastructure must be correctly configured. Klaviyo requires a dedicated sending domain to be authenticated via DNS records. This involves adding CNAME records for DKIM (DomainKeys Identified Mail) and a dedicated return-path.
Authentication acts as your digital signature, proving that the email actually originated from your brand. You should also ensure your SPF (Sender Policy Framework) record is correctly formatted and that you have a basic DMARC policy in place. These protocols are no longer optional; major providers now enforce strict authentication standards for bulk senders. Using monitoring tools like SenderSignal can help you verify that these records are correctly propagated before you begin the ramping phase.
The Engagement-First Strategy
In the initial stages of a warmup, volume is secondary to engagement. MBPs look for positive signals such as opens, clicks, and replies to determine if your mail is wanted. Conversely, negative signals like bounces, unsubscribes, and spam complaints carry significantly more weight during the warmup period.
To maximize positive signals, start by targeting your most engaged segments. This typically includes:
- Customers who have made a purchase in the last 30 to 60 days.
- Subscribers who have opened or clicked an email in the last 30 days.
- New sign-ups from your website who have just opted in.
Avoid sending to your entire list immediately. Even if your list is 100% opt-in, older segments that have not engaged recently are more likely to result in hard bounces or spam reports, which can derail a warmup in its first week.
Recommended Ramping Schedule
A typical warmup follows a doubling pattern or a conservative growth curve. While every brand is different, a general framework for a daily sender might look like this:
- Days 1-2
- Send to a maximum of 50-100 highly engaged subscribers.
- Days 3-4
- Increase volume to 500 subscribers.
- Days 5-7
- Move to 1,000-2,000 subscribers.
- Week 2
- Increase volume by 20% to 50% every other day, monitoring for any drops in open rates.
- Week 3 and Beyond
- Continue expanding the engagement window (e.g., from 30-day openers to 60-day openers) until you reach your full list size.
During this period, it is helpful to pause non-essential automated flows that might cause unpredictable volume spikes. However, high-intent flows like Abandoned Cart and Welcome Series should remain active, as they naturally generate the high engagement rates that help build your reputation.
Monitoring Deliverability Metrics
During a Klaviyo warmup, your performance metrics are your primary feedback loop. You must monitor these daily to catch issues before they become permanent reputation damage. Key benchmarks to watch include:
- Open Rates
- Aim for 30% or higher during the warmup. If opens drop below 20%, it is a sign that providers may be throttling your mail or placing it in the spam folder.
- Bounce Rates
- Hard bounces should stay below 0.5%. High bounce rates indicate poor list hygiene and are a major red flag for MBPs.
- Spam Complaints
- These should be near zero, ideally below 0.1%. A single spike in complaints can halt your warmup progress.
If you notice a decline in performance, the correct response is to 'throttle back.' This means staying at your current volume or even reducing it for several days until your engagement metrics stabilize. Using a platform like SenderSignal allows you to track these placement trends across different providers, ensuring that a delivery issue at Gmail doesn't go unnoticed while your Outlook delivery remains stable.
Managing Automated Flows and Campaigns
Klaviyo users often struggle with balancing one-off campaigns and automated flows during a warmup. Flows are beneficial because they are triggered by user behavior, meaning the recipient is already thinking about your brand. This leads to higher click-through rates.
When calculating your daily volume for the ramping schedule, you must include the volume generated by flows. If your daily limit is 1,000 emails and your flows account for 400, your manual campaign should only be sent to 600 people. As you progress, you can slowly integrate broader segments into your weekly newsletters. Always prioritize the flows that have historically performed the best, as they provide the 'reputation buffer' needed to experiment with larger segments.
Cleaning the List for the Final Push
The final stage of a Klaviyo warmup involves reaching the 'unengaged' or 'win-back' segments of your list. This is the most dangerous part of the process. Before attempting to mail these users, run a final list cleaning process. Remove any addresses that have not engaged in over 6 to 12 months, and consider using a third-party verification tool to identify dormant or invalid mailboxes.
If the warmup was successful, your dedicated domain will now have a established history. However, deliverability is not a 'set and forget' task. You must maintain consistent sending patterns. Large gaps in sending (more than 2-3 weeks of silence) can cause your reputation to 'cool off,' requiring a mini-warmup period when you return to high-volume sending.
Conclusion
A disciplined Klaviyo warmup is an investment in your brand's long-term revenue. By focusing on high-engagement segments and gradually scaling volume, you build a resilient sender reputation that can withstand the high-traffic demands of peak ecommerce seasons. Consistent monitoring and technical verification remain the best defenses against the spam folder.