Email Warm-Up

Email warm-up solves a critical deliverability problem: new email addresses or domains have zero reputation with email providers. When you suddenly send 10,000 emails from a brand-new address, spam filters treat it as suspicious activity and route messages to junk folders—even if your content is legitimate. Think of it like a new restaurant opening: you start with a soft opening for friends and local customers, build word-of-mouth and reviews, then do the grand opening. Email warm-up works the same way.

The process typically involves sending a small number of emails (5-20 per day initially) to engaged recipients—ideally people who open and reply to your messages. Over 2-4 weeks, you gradually increase volume while monitoring open rates, click rates, and bounce rates. Email service providers like Gmail and Outlook track these signals to determine if you're a trustworthy sender. High engagement signals (opens, clicks, replies) tell them your mail is wanted; bounces and spam complaints tell them it's not.

In practice, this shows up in tools like Lemlist, Outreach, and Apollo, which automate warm-up sequences. They'll send initial emails to a small list, pause based on engagement metrics, then incrementally increase sends. Some platforms use AI to personalize early messages, increasing reply rates and accelerating reputation building.

For CMOs buying email or outreach tools, warm-up capability is a hidden but critical feature. Without it, your new domain or sender address will land in spam folders regardless of message quality. This directly impacts campaign ROI—a 40% deliverability rate versus 95% is the difference between a successful campaign and wasted budget. Ask vendors about their warm-up protocols and whether they're included in your plan.