What is the best IP warmup strategy for a new domain on an existing IP?
Michael Ko
Co-founder & CEO, Suped
Published 14 Jun 2025
Updated 17 Aug 2025
7 min read
Warming up a new domain, even when you are using an existing and well-established IP address, is a critical step for email deliverability. While your IP may have a stellar reputation, your domain essentially starts from scratch in the eyes of mailbox providers. This means it has no prior sending history associated with it, making it look like a potential risk.
Mailbox providers, such as Gmail and Outlook, maintain separate reputations for IPs and domains. Your existing IP has a history of good sending, but your new domain needs to build its own trust by demonstrating consistent, wanted email sending behavior. Skipping this process can lead to significant deliverability issues, including emails landing in the spam folder or even outright rejection.
Therefore, even with a warmed IP, a strategic approach to warming your new domain is essential. This strategy involves carefully scaling your sending volume, maintaining high engagement, and closely monitoring performance. It is a nuanced process that requires patience and attention to detail to ensure your messages reliably reach the inbox.
The importance of domain warming
While an IP address serves as the identifiable address for your outgoing mail server, the domain represents your brand's identity as a sender. Mailbox providers assess both. Even if your IP is trusted, a new domain has no established history or trust with them. This lack of history can cause mailbox providers to treat your emails with suspicion, leading to poorer inbox placement.
Think of it this way: your IP is the reliable postman, but your domain is a new company sending mail. The postman (IP) is known, but the new company (domain) still needs to prove its legitimacy. Your domain's reputation is built on factors like subscriber engagement, complaint rates, bounce rates, and whether recipients mark your emails as spam. This process is distinct from building IP reputation.
Therefore, even when an IP is already warmed, neglecting the domain warming process can lead to significant deliverability challenges. The domain needs its own gradual introduction to the email ecosystem to earn trust and avoid being blocklisted (or blacklisted) or filtered into the spam folder. Understanding the distinction between IP and domain warm-up is fundamental for long-term success.
Crafting your domain warmup strategy
The cornerstone of a successful domain warm-up is to start small and gradually increase your sending volume. This mimics organic sending behavior and allows mailbox providers to observe consistent, positive engagement from your new domain. Begin by sending to your most engaged and active subscribers, as these individuals are most likely to open, click, and interact with your emails, sending positive signals to ISPs.
A common practice is to start with a very low volume, such as a few hundred emails, on the first day. Over the subsequent days and weeks, you can incrementally increase the volume, often by 10-20% daily, depending on performance. This slow and steady approach helps build trust and avoids triggering spam filters that might flag sudden, large volumes from an unknown domain.
Additionally, ensure your sending is consistent. Sporadic sending, even at low volumes, can hinder the warming process. Regular daily sends, or at least consistent sends on scheduled days, help establish a predictable pattern that mailbox providers learn to trust. For more detailed information, consider reviewing AWS's dedicated IP warming documentation, which offers valuable insights into the principles of gradual volume increases, applicable even when only warming a new domain.
List segmentation: Send to your most engaged subscribers first. These are the people who have recently opened or clicked your emails.
Clean list: Ensure your list is free of invalid or inactive addresses to avoid bounces and spam traps, which can harm your new domain's reputation.
Content quality: Send highly relevant and engaging content that encourages opens, clicks, and replies.
Consistent sending: Maintain a regular sending schedule, ideally daily during the initial weeks of warming.
Monitoring and troubleshooting deliverability
Monitoring your email deliverability during the warming phase is paramount. Pay close attention to key metrics such as open rates, click-through rates, bounce rates, and, most importantly, spam complaint rates. A sudden spike in complaints or a drop in engagement can signal a problem and may require you to pause or even reduce your sending volume temporarily.
Utilize Postmaster Tools from major mailbox providers like Google and Outlook. These tools provide valuable insights into your domain's reputation, spam rates, and deliverability performance. They can help you identify specific issues with certain providers and allow you to react quickly if problems arise, such as being placed on a blacklist or blocklist.
If you observe emails going to spam, especially during the early stages, do not panic. This can be normal with new domains. However, if the trend persists, consider slightly reducing your sending volume and focusing even more on sending to your most engaged segments. Analyze your content for potential spam triggers and ensure your email authentication (SPF, DKIM, DMARC) is correctly configured, as this can significantly impact your domain's trustworthiness.
Symptoms of issues
High spam rate: A large percentage of your emails are landing in the spam folder.
Low open/click rates: Recipients are not interacting with your emails as expected.
Bounce spikes: An increase in hard or soft bounces, especially at major providers.
Actions to take
Reduce volume: Immediately scale back your sending volume if issues arise.
Once your new domain is warmed and you're consistently reaching your desired sending volumes with good inbox placement, the work isn't over. Maintaining a strong sender reputation is an ongoing process that requires continuous attention to best practices. This includes regular list hygiene to remove unengaged subscribers, bounces, and potential spam traps.
Continue to prioritize sending relevant and engaging content to maintain high interaction rates. Consistently monitor your sender reputation through Postmaster Tools and other analytics. Be proactive in addressing any dips in performance or increases in complaint rates.
Adhering to best practices for email authentication, respecting unsubscribe requests, and maintaining a positive sender score will ensure your new domain retains its good standing. Remember, deliverability is dynamic, and consistent effort is key to long-term success.
Views from the trenches
Best practices
Start with your most engaged subscribers to generate positive signals early on.
Segment your audience by mailbox provider to identify specific deliverability issues.
Maintain a consistent sending schedule throughout the warming period.
Prioritize sending high-quality, relevant content to encourage positive engagement.
Monitor key metrics like open rates, click-through rates, and complaint rates daily.
Common pitfalls
Sending too large a volume too quickly, especially in the initial days.
Ignoring early signs of poor deliverability, such as emails going to spam.
Not segmenting your audience and sending to disengaged users during warmup.
Failing to clean your email list of invalids and unsubscribes beforehand.
Becoming inconsistent with sending volume or frequency after starting warmup.
Expert tips
It is not uncommon for mail to initially land in the spam folder during the early stages of a domain warmup.
An initial daily sending volume of 50 emails is often too low to gather useful performance data.
Consider starting with a daily volume of 100 to 1,000 emails, depending on your total list size.
The first 30 days of any domain warmup often involve some fluctuations in deliverability.
If emails are going to spam, check which specific mailbox providers are affected.
Expert view
Expert from Email Geeks says that it is not unusual for emails to land in spam folders during the initial stages of IP warmup. It is recommended to continue increasing volume by about 30% daily, but to pause volume increases if significant issues arise.
2024-04-10 - Email Geeks
Expert view
Expert from Email Geeks recommends identifying which specific mailbox providers are directing emails to spam. With small volumes, statistics might not be conclusive, and although persistence can help, targeted problem identification is crucial.
2024-04-10 - Email Geeks
Final thoughts on domain warmup
Warming up a new domain on an existing, warmed IP address is a distinct process focused on building domain-specific trust with mailbox providers. It requires a thoughtful strategy that prioritizes gradual volume increases, consistent sending, and high recipient engagement. By focusing on these elements and closely monitoring your deliverability metrics, you can successfully establish a strong reputation for your new domain.
Patience and persistence are key. There might be initial bumps, but by adhering to best practices and promptly addressing any issues, your new domain will eventually earn the trust needed for optimal inbox placement. This ensures your email program continues to deliver results without being hindered by deliverability challenges.
Gmail and 
Outlook, maintain separate reputations for IPs and domains. Your existing IP has a history of good sending, but your new domain needs to build its own trust by demonstrating consistent, wanted email sending behavior. Skipping this process can lead to significant deliverability issues, including emails landing in the spam folder or even outright rejection.
