The gradual process of building sending reputation for a new email domain or IP address by slowly increasing send volume over time, rather than sending a large volume of email immediately from a brand-new sending identity.
Why it matters
Mailbox providers are naturally suspicious of a new sending domain suddenly sending high volumes of email, which can trigger spam filtering — a proper warm-up period establishes a track record of legitimate sending behavior before scaling up to full volume.
In a sentence
"We warmed up the new sending domain over three weeks, starting with our most engaged segment, before moving the full list over."
Related terms
- Often confused with: Deliverability (Part One, Category 5) — warm-up is a specific practice used to establish and protect deliverability for a new sending domain; deliverability is the broader, ongoing outcome that warm-up, list hygiene, and other practices all contribute to).
- Synonyms: IP warming, domain warming.