Do new domains on shared IPs need warming for transactional emails?
Matthew Whittaker
Co-founder & CTO, Suped
Published 11 May 2025
Updated 16 Aug 2025
6 min read
When launching a new email program, especially for transactional emails, a common question arises: do new domains on shared IPs need warming? It's a nuanced topic, often leading to confusion between IP warming and domain warming. While shared IP addresses are generally considered pre-warmed by the email service provider (ESP), a brand-new domain presents its own set of challenges, regardless of the underlying IP infrastructure. I often find this is where senders can run into unexpected deliverability issues.
The distinction between IP and domain reputation is critical. Mailbox providers assess both when deciding whether to deliver your emails to the inbox, spam folder, or reject them entirely. A new domain starts with no history, good or bad, meaning it lacks the established trust that warmed IPs typically possess. This lack of history can lead to caution from mailbox providers, even for essential transactional messages.
The unique challenges of new domains
While shared IPs are often managed and warmed by the ESP, building a positive reputation for the IP itself, your domain's reputation is entirely separate. A new domain (or subdomain) has no prior sending history, no established trust with internet service providers (ISPs), and no track record of low spam complaints or high engagement. This zero reputation state makes it a target for increased scrutiny from spam filters.
Even though transactional emails are expected and often critical, they are not immune to reputation issues. If a new domain immediately sends a high volume of emails, even transactional ones, it can trigger spam filters due to the sudden, unproven activity. This is why warming up your domain is crucial, regardless of the IP type.
The goal of domain warming is to gradually build a positive sending history and establish trust with mailbox providers. This process involves slowly increasing the volume of emails sent from the new domain over time. It signals to ISPs that you are a legitimate sender and allows them to observe recipient engagement patterns, which are vital for reputation building. Failing to warm up a new domain can lead to emails landing in the spam folder, or even being blocked (or blacklisted) entirely.
Shared IP
IP warming: Typically not required, as the ESP manages the IP's reputation across multiple senders.
Domain warming: Essential for new domains, even for transactional emails, due to lack of prior history.
Deliverability impact: Initial deliverability risks are primarily tied to domain reputation.
Transactional emails, by nature, are often triggered in real-time by user actions (e.g., password resets, order confirmations). This makes a strict, controlled sending schedule for domain warming challenging, unlike marketing emails where volume can be ramped up gradually. However, the principle of starting small and increasing volume still applies to new domains for transactional sending. We call this a passive warm-up, where the natural growth of user sign-ups or actions dictates the sending volume.
If a new domain is expected to send a high volume from day one, like tens of thousands of emails, it's generally too much volume for a brand-new domain without any prior reputation. Even for transactional mail, such a burst can lead to deliverability issues. Mailbox providers might view this sudden high volume as suspicious, increasing the likelihood of messages being sent to spam or outright blocked. This is a common pitfall that can harm your domain reputation.
One effective strategy, if applicable, is to use a subdomain of an existing, well-warmed domain for transactional emails from the new service. An established parent domain can lend some of its reputation to a new subdomain, potentially improving initial inbox placement. However, this isn't always feasible, especially if the new CRM instance is designed to be completely separate.
It's also important to verify with your CRM or ESP provider whether their shared IP infrastructure can handle your projected volumes. Some shared IP pools are designed for lower volumes, and exceeding those limits can lead to deliverability problems for all senders on that IP, potentially resulting in your emails being blocklisted (or blacklisted).
Key takeaways for deliverability
In summary, while shared IPs generally don't require explicit IP warming, a new domain always benefits from a warming period, even for transactional emails. The goal is to build a positive sending reputation gradually. This might involve starting with lower volumes and letting organic subscriber growth dictate the ramp-up. If high initial volumes are unavoidable, consider leveraging a subdomain of an existing, well-reputed domain.
Monitoring your domain's reputation using tools like Google Postmaster Tools is essential throughout this process. Pay close attention to spam complaint rates, bounce rates, and overall deliverability. If you see signs of trouble, it may indicate that your domain is being viewed with suspicion, and you might need to further adjust your sending volumes or strategy. Proactive monitoring can help you identify and address issues before they escalate into major deliverability problems.
Navigating the complexities of email deliverability with new domains on shared IPs requires careful planning and continuous vigilance. Understanding the distinct roles of IP and domain reputation can help you ensure your critical transactional emails reach their intended recipients.
Views from the trenches
Best practices
Start with very low sending volumes for a new domain and gradually increase over time to build sender trust.
Utilize a subdomain of an already warmed, established domain for new services to leverage existing reputation.
Actively monitor your domain's reputation using available tools to catch deliverability issues early.
Ensure your ESP or CRM provider is equipped to handle projected high volumes on shared IP infrastructure.
Focus on maintaining low complaint rates and high engagement from the outset to bolster domain health.
Common pitfalls
Sending high volumes immediately from a new domain, even transactional, without any warm-up period.
Assuming shared IP warming negates the need for new domain warming, leading to poor deliverability.
Not accounting for the real-time, often uncontrollable, nature of transactional email volume during warm-up.
Failing to check with your ESP whether their shared IP is suitable for your expected email volumes.
Ignoring initial signs of deliverability problems, such as high bounce rates or increased spam folder placement.
Expert tips
Passive domain warming through organic subscriber growth is often the most natural approach for transactional emails.
A new domain sending bulk messages within three months of registration can face significant scrutiny from mailbox providers.
While IP warming isn't for shared IPs, domain warming is always needed for a new domain.
The aggressiveness of a domain warming plan depends on expected volumes, cadence, and domain history.
Introducing a new domain without an introductory period can lead to deliverability issues at major consumer mailboxes.
Expert view
Expert from Email Geeks says that you cannot warm a shared IP, but a brand new domain still requires warming, with the intensity depending on the expected sending volumes.
2022-05-09 - Email Geeks
Marketer view
Marketer from Email Geeks says that it's always advisable to warm up any new email configuration, starting slowly and gradually increasing volume, as they have observed issues when new domains were introduced without an introductory period.
2022-05-09 - Email Geeks
Conclusion
In the world of email deliverability, the assumption that shared IPs automatically negate the need for domain warming for new domains can be a costly mistake. While shared IPs indeed come with a pre-established reputation for the IP itself, your domain's individual standing with mailbox providers is built from scratch. For transactional emails, which are often time-sensitive, this initial lack of trust for a new domain can directly impact critical user experiences.
Therefore, even with shared IPs, domain warming remains a vital step. A gradual, controlled rollout of email volume helps new domains establish a positive sender reputation and avoid common pitfalls such as hitting spam traps or being prematurely added to a blocklist (or blacklist). Prioritizing domain warming for new sending domains is an investment in long-term deliverability success and sender trust.
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