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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, warm up your domain and/or IP. This applies when you use a new domain, a new IP, or a new vendor, or when your volume will increase. 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.

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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.

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Warm-up calculator

Use the calculator below to generate a personalized warm-up schedule based on your specific needs. Enter your target volume, timeline, and domain type to get a custom plan. The guide is meant as a general plan, but always pay careful attention to your deliverability and adjust accordingly. If you have specific questions, please reach out to us.

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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. Resend provides an automatic warm-up process so that you can focus on sending. Learn more about requesting a Dedicated IP.

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Third-party warm-up services

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, focus 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.