Warm your client’s sending infrastructure
Warming your client's account is equal parts art and science. Whether your client is eager to send to their entire list on day one or staring at you with confusion, you're on the hook for building a plan that knows where to start, how to ramp, and when to open the full list.
What is warming?
Warming is the process of gradually increasing your sending volume to prove to inbox providers, Gmail, Yahoo, Outlook, that your emails are legitimate and wanted. This video walks through what warming means.
Build your warming plan
Remember planning a birthday party as a kid? You'd invite the whole class and hope for the best. As you got older, the guest list got more intentional: close friends who you knew would actually show up. That's warming. You start with the people most likely to engage, build a reputation with inbox providers, and prove you're a trustworthy sender.
Unlike a birthday party though, the goal isn't to keep the guest list small forever. Once you've built that reputation, you earn the right to reach further: the occasional customer, the casual browser, or the person who opened once six months ago. That's ramping.
Here is what a typical warming and ramping plan look like:
Before you build anything, ask your client to export their last open date and last click date from their previous ESP and import them into Klaviyo as profile properties.
Once imported, build your warming audiences in this order:
- Clicked in the last 30 days
- Opened or clicked in the last 30 days
- Opened or clicked in the last 60 days
- Opened or clicked in the last 90 days
- Opened or clicked in the last 180–365 days (only once your metrics are consistently strong)
If any of these segments are larger than your target send volume, pull a sample.
Note: samples are created as lists by default, so convert each one to a segment so that unsubscribes route to your master list and not a sample specific one.
Once you know your audiences, map them to a send schedule using these rules:
- Starting volume: 2,000 to 5,000 profiles. If the list is smaller than that, start with about a third of your full list.
- Volume increases: Never more than 2x from one send to the next.
- Cadence: 2 to 4 times per week. Gaps weaken the reputation you are building.
- Gate every increase on performance: Only move to the next volume tier once the previous send hit open rate above 25–30%, bounce rate below 0.5%, and spam complaints near zero.
- Audience boundary: Do not expand beyond 90-day engaged contacts in the first month unless metrics are consistently strong.
💡 Find your North Star first: Before you build the schedule, ask your client how many people they normally send to. That number, not the full list, is your target. If they typically send to 50,000 out of 200,000 profiles, build the ramp toward 50,000.
Warming in practice: four real examples
The plan is science. How you execute it is art. Here are three real examples of the challenges you are most likely to encounter and how to handle them.
Example 1: Limited data
Situation: Mid-size ecommerce brandOutcome: Smooth
Without reliable open and click data from the previous ESP, standard engagement segments weren't possible. The team used behavioral signals instead, recent purchasers, high-intent browsers, and checkout abandoners, as a proxy for engagement. Early sends were capped at around 5,000 profiles and focused on high-intent promotions rather than broad newsletters to maximise those critical first open rates. Once Klaviyo had its own engagement data, later waves could use standard segments. The art was redefining "engaged" when legacy data wasn't there.
Key takeaway: Ideally you can use engagement data, but if your client's previous ESP didn't capture reliable open and click data, look to behavioral signals like purchases, product views, checkout events.
Large List + Dual Send
Situation: Large global retailer (~240k active subscribers) migrating to Klaviyo with daily sends still running from the legacy ESP
Outcome: Smooth
Historic open rates around 60% enabled an unusually fast two-week ramp. The legacy ESP kept running in parallel: as each cohort migrated into Klaviyo, those profiles were suppressed in the old ESP to prevent duplicate sends. To keep content pressure manageable, the plan used three to four reusable templates rather than new creative for every send. One mid-ramp issue required adaptation: Gmail was clipping heavy campaigns, hurting tracking and engagement, resolved by tightening templates and moving the tracking pixel.
Key takeaway: Dual sending works when ownership is clear: the client manages exclusions in the old ESP, you own the strategy. Check template weight early: emails clipped by Gmail will hurt your metrics at the worst possible time.
Example 3: Rebranding
Situation: Small boutique brand | Outcome: Smooth
A new domain meant zero sending history, and inbox providers had no basis for trust. The team sent a text-based notification from the old domain first, leading with the familiar brand name so subscribers could recognize the sender and understand what was changing. Early sends on the new domain were kept small, starting with the most engaged subscribers, and volume increased gradually over several weeks. Flows were set to draft, updated to reflect the new branding, and reactivated once the domain had traction.
Key takeaway: A new domain is a blank slate to inbox providers regardless of how established the brand is. Notify customers on your old domain before you switch, start small, and warm your infrastructure before scaling sends. This article here walks through how to rebrand a domain.
Example 4: Prior Reputation Issues
Situation: Large franchise brand with millions of profiles and prior deliverability problems in specific inbox providers Outcome: Recovered
Mid-warm, a bounce spike appeared at regional inbox providers. Segments were tightened to recently engaged contacts only, legacy ESP suppression lists were audited for anything that may have carried over, and volume growth paused until metrics stabilised. Monitoring caught the issue early which is exactly how this is supposed to work. A note for enterprise onboardings: other channels like SMS can create their own compliance workstreams running in parallel to email warming, so keep that in mind if you are onboarding more than just email.
Key takeaway: Prior reputation issues don't prevent a successful warm-up, they just require faster response times. When signals spike, tighten segments and audit suppressions first. At enterprise scale, loop in your deliverability contacts early.
Creating a warming plan is one of the most important pieces of a successful Klaviyo onboarding engagement. If you are curious what a warming schedule looks like, check out the example warming schedule in our onboarding project plan