Warming up a domain or IP refers to the practice of progressively increasing your sending volume to maximize your deliverability. The goal is to send at a consistent rate and avoid any spikes in email volume that might be concerning to inbox service providers. Whenever you change your sending patterns—whether because you’re using a new domain, a new IP, or a new vendor, or because your volume will increase—you should warm-up your domain and/or IP. A thought-out warm-up plan limits greylisting and delivery throttling, as well as helping establish a good domain and IP reputation. As your volume increases, you’ll need to monitor your bounce rate to ensure it remains below 4%, and your spam rate below 0.08%. An increase in these rates would be a sign that your warm-up plan needs to be slowed down and an investigation into the root causes of the increases started. Following these rules and metrics will establish a good domain reputation.
Each sender has different constraints and needs, so these numbers are meant as a baseline. Our Support team can work with you on devising a plan adapted to your needs.

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Existing domain

If you’re already sending from an existing domain with established reputation and volumes, you can use the following guidelines to start sending with Resend.
DayMessages per dayMessages per hour
1Up to 1,000 emails100 Maximum
2Up to 2,500 emails300 Maximum
3Up to 5,000 emails600 Maximum
4Up to 5,000 emails800 Maximum
5Up to 7,500 emails1,000 Maximum
6Up to 7,500 emails1,500 Maximum
7Up to 10,000 emails2,000 Maximum

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New domain

Before you start sending emails with a brand new domain, it’s especially important to have a warm-up plan so you can maximize your deliverability right from the start.
DayMessages per dayMessages per hour
1Up to 150 emails
2Up to 250 emails
3Up to 400 emails
4Up to 700 emails50 Maximum
5Up to 1,000 emails75 Maximum
6Up to 1,500 emails100 Maximum
7Up to 2,000 emails150 Maximum

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Warming up your Dedicated IP with Resend

In order for a Dedicated IP to be beneficial or useful, you first need to establish a certain sending volume and patterns. Once you’ve established this volume and these patterns, our Support team can set it up for you. We provide an automatic warm-up process so that you can simply focus on sending. Learn more about requesting a Dedicated IP.

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What about third-party warm-up services?

We know email deliverability is important, and it can be tempting to use services promising quick fixes. However, using tools that artificially boost engagement can harm your long-term sender reputation. These services often rely on manipulating anti-spam filters, which can backfire as email providers like Gmail adjust their systems. Instead, we recommend focusing on sustainable practices—such as sending relevant content, maintaining a clean list, and using proper authentication. These methods build trust with email providers and improve your deliverability over time.