Domain warmup is the process of gradually establishing a positive sending reputation for a new email domain before sending high volumes of email. When you get a new domain and immediately blast thousands of emails, inbox providers like Gmail and Outlook flag you as a potential spammer because you have no sending history. Domain warmup involves starting with small send volumes to engaged recipients, gradually increasing volume over days or weeks, and maintaining good engagement metrics so inbox providers learn your domain sends legitimate email that people want. This is critical for email deliverability and avoiding the spam folder.
Why Warmup Prevents Deliverability Issues
Inbox providers are looking for suspicious patterns that indicate spam. A brand new domain suddenly sending 10,000 emails per day is suspicious. But a domain that starts with 50 emails per day to engaged recipients, grows to 100 the next day, then 200, then 500, and shows consistent positive engagement looks legitimate. The warmup period proves to inbox providers that you’re a real sender with real recipients who want your emails. Skip the warmup and you’ll end up in spam immediately, your domain reputation will be damaged, and recovering from that is way harder than doing the warmup right in the first place.
Running A Proper Warmup
A proper domain warmup takes two to four weeks depending on your target send volume. You start by sending only to your most engaged subscribers who are most likely to open and click. You gradually increase volume by 50% to 100% per day or every few days. You monitor your engagement metrics closely and slow down if open rates or click rates drop. You avoid spam trigger words and you include proper authentication like SPF, DKIM, and DMARC from the start. Many businesses use warmup tools that automate this process by simulating real email activity to build reputation faster. The goal is reaching your target send volume with a strong sending reputation that keeps you out of the spam folder.