What is email warm-up?
Also called: IP warm-up, domain warming, inbox warm-up
Email warm-up is raising sending volume gradually on a new domain, inbox or IP address so mailbox providers can build a reputation for it before full volume arrives. Sending thousands of messages from an identity with no history is one of the most reliable ways to land in spam.
Providers have no data on a new sending identity, and the cautious assumption about a sudden high volume is that it is spam. Warming replaces that absence with a record: small volumes, few bounces, real engagement, increasing over several weeks.
The exact schedule matters less than the signals. Replies and opens during warm-up are what build reputation, which is why warming against an unverified list defeats itself: the bounces teach the provider exactly the wrong thing.
Verify the list before warm-up, not after. There is no point spending weeks building reputation on addresses that do not exist.
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By SimpleVerifier Team · Last reviewed 2026-10-13 · All 50 glossary terms