Every day, Mailchimp delivers around 600 million emails to users who expect their campaigns to arrive immediately. Meeting these high expectations requires a highly optimized system designed for speed and reliability. To achieve this, Mailchimp breaks down large email campaigns into manageable pieces, ensuring fast and efficient delivery without overwhelming the infrastructure.
When you click Send in the Campaign Builder, you’re actually instructing Mailchimp to start processing your campaign in smaller “payloads.” Instead of handling one massive batch, the system divides the campaign into these smaller segments. Each payload is instantly routed to Mail Transfer Agents (MTAs), where they are queued and sent out in a prioritized manner. The system organizes recipients based on their engagement level, so the most active and interested subscribers receive their emails first. This prioritization improves open rates and overall campaign effectiveness.
For very large campaigns, each payload usually contains about 10,000 recipients. By working with smaller payloads rather than waiting for one huge batch—sometimes hundreds of thousands of recipients—to be created and processed, Mailchimp can start delivering emails immediately. This approach reduces delays and helps ensure that campaigns reach inboxes faster, maintaining the high standard users expect from Mailchimp’s service.
Overall, this method of breaking campaigns into smaller parts and prioritizing recipients allows Mailchimp to handle enormous volumes of email every day with speed, precision, and reliability.