Contents
The short answerDo you need to warm?The scheduleReading the metricsQuestionsRelated service
Klaviyo →The short answer
A new sending domain earns inbox placement by sending small, to the most engaged slice of the list, and expanding only as the results hold: 30-day engaged first, then 60, 90 and beyond, each window earned by the one before, over four to eight weeks. Not every change needs it, and the first decision is whether you are warming at all.
Why warming matters
Inbox providers have no history for a new sending domain, so there is nothing for them to evaluate, no reputation and no record of how recipients have responded before. When a fresh domain sends a large volume immediately, it looks identical to a spam operation setting up a new identity.
Warming builds reputation by starting small, with the most engaged subset of the list, and expanding as the engagement holds. Inbox providers watch the pattern of opens, clicks and complaints, and they extend inbox placement to larger sends as the pattern proves consistent.
Do you need to warm at all?
Klaviyo's own guidance separates the cases, and the distinction saves brands weeks of unnecessary caution. A domain registered within the last month, or never used for email, warms in full. A new Klaviyo account on a domain with real sending history warms the platform transition more briefly. And an existing Klaviyo customer adding a branded sending domain to a domain that has been registered for more than 30 days and already sends email does not need to re-warm at all, because the reputation follows the domain rather than the settings page.
The expensive mistake runs in both directions: full-warming an established domain wastes a month of revenue on caution nobody required, while blasting a fresh domain because "the list is opted in" builds a spam-folder reputation that takes far longer to repair than warming would have taken to do.
The expansion schedule
The first sends go to the 30-day engaged segment, subscribers who have opened or clicked in the last month, and Klaviyo recommends keeping the first campaign under 10,000 recipients even when the engaged list is larger.
| Stage | Audience | Condition to advance |
|---|---|---|
| Weeks 1 to 2 | 30-day engaged, capped small | Opens holding above roughly 20 percent, complaints near zero |
| Weeks 3 to 4 | 60-day engaged joins | The same results holding at the larger volume |
| Weeks 5 to 6 | 90-day, then 120-day engaged | Steady metrics, no provider deferrals |
| Weeks 7 onward | 180-day engaged completes the sendable list | Full history of consistent engagement |
If open rates dip below the line at any stage, the audience tightens back to the more engaged windows until they recover, and the schedule restarts from there rather than pushing through. Klaviyo treats four weeks as the minimum before the audience scope widens meaningfully, a full progression often runs eight weeks or more, and unengaged contacts stay out of the picture entirely until the domain has a solid record.
What to send while warming
Warming sends should be the mail your engaged subscribers most reliably open, which usually means the strongest editorial and new-arrivals content rather than discount blasts, on a steady rhythm of two or three sends a week. Flows have their own order too: switch the high-engagement flows, welcome and post-purchase, to the new domain early, and let the volume-heavy flows follow as the reputation builds.
Klaviyo's guided warming can manage the ramp automatically for flows when a new domain is set up, throttling the volume up over time, and it is worth understanding what it covers so campaign sending gets the manual schedule above rather than an assumption that the platform is handling everything.
The point of all of it is to show inbox providers one consistent pattern, a sender who sends to people who open. Held long enough, that pattern becomes the domain reputation that lets future large sends land in the inbox, and the same contraction-and-rebuild logic is how a damaged reputation gets repaired, because building trust and rebuilding it are the same process at different starting points.
Reading the metrics during the ramp
Warming is judged send by send, and three readings decide each advance. Open and click rates by inbox provider, because Gmail, Outlook and Yahoo extend trust independently and a domain can be inboxing at one while the next still filters it. Bounce responses, since deferrals and temporary failures are providers throttling an unproven sender, a normal signal early that should fade week by week. And the spam complaint count, where anything beyond a stray one during warming means the segment definition is looser than it claims.
Set up Google Postmaster Tools on day one, because its domain reputation reading is the closest thing to seeing Gmail's opinion directly, and the record of the ramp is useful evidence for as long as the domain sends.
Questions we hear about warming
The schedule can compress a little with a small, highly engaged list, and the providers set the pace either way. A launch that needs full-list email in a fortnight needs the warming started a month earlier, which is a planning finding rather than a deliverability one.
If the sending domain moves with you and has real history, the domain reputation carries. The platform transition still deserves a brief conservative ramp, because the sending infrastructure behind the domain changes.
Some of it lands, providers read the cold start plus the volume as a spam pattern, and the domain begins life with a filtered reputation. Repairing that costs more weeks than warming would have, from a worse starting point.
Sources & references
- Klaviyo Help Center, How to warm your sending domain(help.klaviyo.com)
- Klaviyo Help Center, Understanding which warming process to use(help.klaviyo.com)
- Klaviyo Help Center, Understanding guided warming(help.klaviyo.com)
- Klaviyo Help Center, How to set up a branded sending domain(help.klaviyo.com)
