Glossary
Domain warmup
Domain warmup is the slow, measured ramp of real mail from a new domain or mailbox so it earns a sending reputation before it is used for outreach.
Warmup is not a trick and it is not a setting. It is a schedule of real messages, sent to a pool of domains that open them, reply, and pull them out of spam, rising over 6 to 8 weeks. The provider sees a mailbox that behaves like a person's, and treats it as one.
The ramp runs roughly 10, 20, 35, 50 and then 60 messages a day per mailbox. Those are targets. The reading decides the real number each day, and the schedule bends to it. A mailbox that is read as healthy moves up; one that dips holds or comes down.
The warmup in an outbound engineering program runs on warming.email, which was built for exactly this. It prepares a domain and hands back one clear number: how much this mailbox can send today.
Questions
Why not skip warmup and start slow?
Because slow real sends to strangers still produce negative votes if the addresses are wrong or the message is unwanted, and a mailbox with no history has no buffer. Warmup builds the buffer first with mail that is answered.
Does warmup end?
The fixed cycle ends. Reading the mailbox never does. Live recipients behave differently from warmup traffic, so the first weeks of real sending are watched as closely as the ramp.
This term belongs to the outbound engineering glossary. The practice is defined on the category page.
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