What Is Domain Warmup?

Domain warmup is the systematic process of gradually increasing email sending volume from a new domain to establish a positive sender reputation with email service providers (ESPs) like Gmail, Outlook, and Yahoo. Without proper warmup, emails sent from new domains are flagged as suspicious and routed to spam folders, regardless of content quality. The warmup process typically takes two to four weeks and involves sending a small number of emails daily — starting with 5-10 per day — and incrementally increasing volume as the domain builds positive engagement signals. During warmup, the goal is to generate opens, replies, and other positive interactions that signal to ESPs that the domain sends legitimate, wanted email. Effective domain warmup requires several technical prerequisites: properly configured SPF, DKIM, and DMARC authentication records, a dedicated IP address or reputable shared IP pool, and consistent sending patterns. Many organizations use warmup services or platforms that exchange emails between accounts to simulate organic engagement. End-to-end platforms like Prospect AI automate the entire warmup process as part of their infrastructure management, ensuring domains reach optimal deliverability before outbound campaigns begin.