Email warmup is the systematic process of gradually increasing the sending volume and building positive engagement signals on a new or dormant email account to establish a strong sender reputation with email service providers. When a new email account starts sending cold outreach immediately at high volumes, inbox providers like Google and Microsoft flag the activity as suspicious and route messages to spam. Email warmup prevents this by simulating natural email behavior over a period of weeks, teaching inbox providers that the account is legitimate and trustworthy.
The warmup process works by sending emails between your account and a network of other real email accounts that are configured to interact positively with your messages. These interactions include opening emails, reading them for a period of time, replying with contextually relevant responses, marking messages as important, moving them from spam to inbox if they are misrouted, and occasionally clicking links within the messages. Each of these engagement signals tells inbox providers that recipients value the emails coming from your account, which builds your sender reputation over time.
A proper warmup schedule typically begins with 5 to 10 emails per day during the first week, increasing to 15 to 25 in the second week, 25 to 40 in the third week, and reaching full sending capacity of 40 to 50 emails per day by the fourth to sixth week. The exact ramp-up speed depends on the email provider, domain age, and existing domain reputation. Domains with established history can often warm up faster than brand new domains.
Email warmup is not a one-time activity. Even after the initial warmup period, ongoing warmup sending should continue alongside cold outreach to maintain healthy engagement metrics. If an account's engagement rates drop due to a poorly performing campaign, warmup emails help counterbalance the negative signals and prevent reputation degradation. ProspectAI's warmup system operates continuously, automatically adjusting the ratio of warmup to cold emails based on real-time account health metrics.
Key metrics monitored during warmup include inbox placement rate (the percentage of emails landing in primary inbox versus spam), sender reputation score, bounce rate, open rate, and reply rate. Healthy accounts maintain inbox placement above 85 percent, bounce rates below 2 percent, and open rates above 40 percent on warmup emails.
Sophisticated warmup systems also simulate realistic conversation patterns rather than sending disconnected one-off messages. These include multi-turn email threads, meeting scheduling discussions, and project collaboration conversations that mirror authentic business communication. This level of realism is important because inbox providers increasingly use content analysis and behavioral patterns to distinguish legitimate email from automated spam.
