What is a email warmup?
Also called: domain warming, IP warming
Email warmup is the practice of raising sending volume gradually on a new domain or IP so mailbox providers build a reputation for it before the full volume arrives. Sending thousands of messages from a domain with no history is one of the most reliable ways to land in spam.
Providers have no reputation data for a new sending identity, and in the absence of data the safe assumption is that a sudden high volume is spam. Warming replaces that absence with a record: small volumes, low bounces, real engagement, increasing over two to six weeks.
A typical schedule starts in the tens of messages a day and roughly doubles weekly, but the number matters less than the signals. Replies and opens during warmup are what actually build reputation, which is why warming to an unverified list is self-defeating — the bounces teach the provider exactly the wrong thing.
Verification belongs before warmup, not after. There is no point spending six weeks establishing a reputation using addresses that do not exist.
Last reviewed 2026-09-11