How to warm a new domain on an already warmed IP address?
Matthew Whittaker
Co-founder & CTO, Suped
Published 27 Jul 2025
Updated 16 Aug 2025
7 min read
Moving to a new domain can feel like a fresh start, but when your IP address is already warmed up, it introduces a unique question: do you still need a domain warming period? This is a common point of confusion. Many email service providers (ESPs) might suggest that since your IP has a strong reputation, your new domain will automatically inherit that trust, meaning you can resume normal sending volumes immediately. However, this advice often overlooks a critical factor in modern email deliverability: domain reputation.
While a warmed IP address provides a solid foundation, internet service providers (ISPs) like Google and Yahoo increasingly scrutinize domain reputation as a primary indicator of a sender's trustworthiness. A new domain is, by definition, an unknown entity to these providers, regardless of the IP it's associated with. Skipping the warming process for a new domain can lead to severe deliverability issues, including emails landing in spam folders or being blocklisted (blacklisted).
Understanding domain reputation
The distinction between IP and domain reputation is crucial. An IP address builds reputation based on the historical sending behavior of all domains using that IP. If your IP has been sending high-engagement, low-complaint emails, it has a good standing. However, the domain (the From address in your emails, like yourbrand.com) has its own separate reputation. This reputation is built on how recipients interact with emails specifically from that domain.
When you introduce a new domain, even on a pre-warmed IP, ISPs see it as an unverified sender. They want to observe how your recipients engage with emails from this new domain before fully trusting it. Without this careful introduction, a sudden surge in volume from a new domain can trigger spam filters, regardless of the underlying IP's positive standing. This means that a domain warming period is absolutely necessary for building this new sending identity.
This practice helps establish credibility for your new domain, ensuring mailbox providers recognize it as a legitimate sender. For more context on the general importance of warming, you can refer to Mailgun's guide on domain warm-up.
Crafting your domain warm-up strategy
While a full IP warming process isn't needed, you should still implement a gradual ramp-up for your new domain. The process will generally be less painstaking than a brand-new IP warm-up because your IP reputation acts as a beneficial underlying factor. The goal is to slowly introduce your new domain to ISPs, allowing them to monitor engagement and build trust. Start with very small volumes to your most engaged subscribers.
You can typically start with a slightly higher volume than you would for a cold IP, perhaps around 500 emails on day one, and then gradually double that volume each day or every other day, depending on your engagement metrics. The speed of your ramp-up should always be dictated by how recipients respond to your emails. If you see dips in open rates, increases in bounce rates, or higher spam complaints, it's a sign to slow down.
Here's a general guideline for volume increase, though this can be adapted based on your specific audience and their engagement:
Day
Approximate volume increase
Day 1
Start with 200-500 highly engaged recipients.
Days 2-7
Increase volume by 100% per day, reaching up to 12,000 emails by week's end.
Throughout the domain warming process, diligent monitoring of your email metrics is paramount. Key performance indicators (KPIs) like bounce rates, spam complaints, and engagement (opens and clicks) will tell you if your warming strategy is effective or if you need to adjust. Ideally, your bounce rate should remain below 2%, and spam complaints should be at or below 0.1%. If you notice a significant increase in unsubscribes, it might indicate that your audience isn't aware of the domain change, which ties into the importance of communication.
It's also essential to keep an eye on your blocklist monitoring and domain reputation through tools like Google Postmaster Tools. Early detection of issues allows you to pause your ramp-up and address any problems before they escalate. A proactive approach to monitoring helps prevent your new domain from being flagged as suspicious by ISPs or landing on a blacklist (or blocklist).
Critical metrics to monitor
Bounce Rate: Keep this below 2% to indicate list hygiene.
Spam Complaint Rate: Maintain at or below 0.1% for positive sender reputation.
Engagement (Opens/Clicks): Ensure engagement rates remain consistent with your previous domain. If they lag, pause or slow down your ramp-up until they improve.
Technical considerations and authentication
Even with an already warmed IP, proper email authentication (SPF, DKIM, DMARC) for your new domain is non-negotiable. These records tell receiving servers that emails from your new domain are legitimate and authorized. Incorrectly configured records can lead to emails being rejected, regardless of your IP's good standing.
If you're using a full Salesforce Marketing Cloud Sender Authentication Package (SAP) domain change, you should coordinate closely with their deliverability team. This might involve having both your old and new domains active for a transitional period to ensure a smooth switch. Furthermore, ensuring that your return-path (SPF) domain matches your From domain is crucial for maintaining proper alignment, which is a key factor in how ISPs assess your sending reputation. A good overview of these protocols can be found in our guide, A simple guide to DMARC, SPF, and DKIM.
Verifying your DNS records for SPF, DKIM, and DMARC is a fundamental technical step. These records ensure that your emails are authenticated correctly, which is vital for building and maintaining domain reputation. A proper DNS configuration signals to receiving mail servers that you are a legitimate sender.
Communicating with your audience
One often overlooked aspect of a domain transition is communicating the change to your audience. Sending a heads-up message from your old domain about the upcoming brand or domain change can significantly reduce confusion, minimize spam complaints, and maintain deliverability. This proactive communication helps set recipient expectations and signals to ISPs that your new domain is part of an expected, legitimate transition, not a sudden, suspicious change.
Consider updating your email headers or footers with a temporary notice weeks before the actual switch. This subtle change can prime your audience and the mailbox providers for the new sending domain. A smooth domain transition directly impacts your overall email deliverability rates and sender reputation, ultimately ensuring your messages reach the inbox consistently.
The path forward
When transitioning a new domain on an already warmed IP, it's a balance between leveraging existing IP trust and meticulously building new domain credibility. While the process may be less arduous than a full IP warm-up, it is by no means optional. A strategic, monitored domain warming approach, coupled with clear communication to your audience, is the key to ensuring continued strong email deliverability.
Views from the trenches
Best practices
Start with a highly engaged segment of your audience for initial sends to generate positive engagement signals for the new domain.
Monitor key email metrics like open rates, click-through rates, bounces, and complaints closely throughout the warming period.
Ensure SPF, DKIM, and DMARC are correctly configured for your new domain before you begin sending.
Coordinate with your ESP's deliverability team, especially for complex transitions like a full Sender Authentication Package (SAP) domain change.
Send a pre-notification email from your old domain to inform subscribers about the upcoming domain change and rebrand.
Gradually increase email volume based on positive recipient engagement and deliverability performance, rather than fixed schedules.
Common pitfalls
Assuming an already warmed IP means no domain warming is needed, leading to sudden high-volume sending from the new domain.
Not monitoring engagement metrics during the warm-up, missing signs of poor domain reputation before it escalates.
Failing to set up proper email authentication (SPF, DKIM, DMARC) for the new domain, causing emails to fail authentication checks.
Neglecting to inform recipients about the domain change, resulting in higher spam complaints or unsubscribes due to confusion.
Increasing sending volume too quickly, overwhelming ISPs and triggering spam filters or blocklists (blacklists).
Not having a rollback plan if deliverability issues arise, leaving you without a clear strategy to recover.
Expert tips
Use a cautious ramp-up schedule, starting small (e.g., 500 emails) and doubling volume daily, adjusting based on engagement.
Maintain consistent engagement stats between your old and new domains during the migration; pause increases if new domain engagement lags.
Ensure the return-path (SPF) domain consistently matches the 'From' domain to strengthen email authentication and alignment.
Leverage engaged segments of your audience initially to build positive signals for the new domain more rapidly.
Consider a dual-domain active period, sending from both the old and new domains simultaneously during the transition.
Implement multi-bounce domain capabilities with your ESP to ensure proper return-path domain matching for deliverability.
Marketer view
A marketer from Email Geeks says that a warm-up is definitely needed for any domain or IP change, but it won't be as painstaking when the IP is already warm. A gradual migration, starting very small (200 messages) and doubling daily for a week, can reach about 12,000 messages per day. After that, a 200% increase per send is possible until the migration is complete. Engagement statistics between the old and new domains must be the same during the migration, otherwise you should pause the ramp-up.
2023-01-06 - Email Geeks
Marketer view
A marketer from Email Geeks says that many providers now heavily rely on domain reputation, so domain warming is crucial.
Google and 
Yahoo increasingly scrutinize domain reputation as a primary indicator of a sender's trustworthiness. A new domain is, by definition, an unknown entity to these providers, regardless of the IP it's associated with. Skipping the warming process for a new domain can lead to severe deliverability issues, including emails landing in spam folders or being blocklisted (blacklisted).
