Definition
Email warmup is the process of gradually increasing a new domain or mailbox's sending volume while generating positive engagement (opens, replies, moves out of spam) to establish sender reputation with mailbox providers. It typically runs for two to four weeks before real outreach begins.
Why it matters
Send at volume from a cold domain and providers treat you as a spammer. Warmup is the unglamorous prerequisite that makes everything downstream actually reach the inbox.
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