What Is Email Warmup?

The process of gradually increasing sending volume from a new email domain or address to build sender reputation with mail servers.

Email warmup is the practice of gradually increasing the volume of emails sent from a new sending domain or email address over several weeks, allowing mail servers to build a positive sender reputation before high-volume campaigns begin.

Why warmup is necessary

Mail servers use sending history as a trust signal. A new domain that sends 500 emails on its first day looks like a spam operation — spam campaigns often use newly-registered domains specifically to avoid reputation consequences. Without warmup, emails from new domains go to spam or are rejected entirely, regardless of content quality.

Warmup schedule

• Days 1–7: 10–20 emails/day (mostly warmup pool emails, few cold emails)
• Days 8–14: 25–50 emails/day
• Days 15–21: 50–100 emails/day
• Days 22–30: 100–200 emails/day
• Day 31+: Up to 500 cold emails/day (conservative safe maximum per domain)

Warmup pools

Most modern cold email platforms offer automated warmup through a "warmup pool" — a network of email accounts that automatically exchange emails with your new sender, open them, move them from spam to inbox, and reply to them. This simulates positive engagement signals that build domain reputation. The warmup pool runs continuously in the background during and after your campaign ramp.

Signs warmup is insufficient

Open rates below 20%, high spam folder placement, and sudden deliverability drops after a volume increase all suggest the domain needs more warmup before scaling further.

Related terms

Put Email Warmup into practice with YOG.io

YOG.io is a governed outbound platform — AI discovers verified contacts, AI drafts personalised sequences, and a human approves before every send.