What Is Email Warmup?
Email warmup is the practice of gradually increasing sending volume from a new or dormant mailbox while generating positive engagement — opens, replies, and moves out of spam — so that mailbox providers learn to trust the sender and route future messages to the inbox.
When a fresh domain or mailbox suddenly sends dozens or hundreds of cold emails, providers like Gmail and Outlook treat the spike as suspicious and often divert those messages to spam. Warmup avoids this by starting with a handful of sends per day and ramping up over several weeks, mimicking the pattern of a genuine human correspondent.
Modern warmup tools automate this by exchanging emails between a network of real mailboxes. Recipients open the message, reply, and mark it as important or rescue it from spam — all signals that tell the provider the sender is legitimate. A typical ramp runs from ~5 emails/day up to 40–50/day over 3–4 weeks before a domain is considered outreach-ready.
Warmup is not a one-time task. Established senders keep a portion of warmup traffic running continuously to maintain reputation between campaigns and to recover quickly after a deliverability dip.
MailPilot automates progressive warmup across a network of real peer mailboxes, then shows you an outreach-ready status so you know exactly when your domain is safe to scale.
See how MailPilot warmup works →