How to warm up a new domain for 6k active contacts when moving from a shared domain to a private domain?
Michael Ko
Co-founder & CEO, Suped
Published 23 May 2025
Updated 15 Aug 2025
8 min read
Moving from a shared sending domain to a private one is a significant step towards greater control over your email deliverability. With 6,000 active contacts and respectable open rates (17-25%), your email program shows promise, but this transition, especially when influenced by platform changes like those from Microsoft, requires careful planning. A new private domain starts with no prior sending history or reputation, making the warming process critical to avoid deliverability issues.
The goal of domain warming is to gradually build a positive sender reputation with internet service providers (ISPs) and mailbox providers, such as Gmail and Outlook. This involves slowly increasing your sending volume over time, ensuring high engagement rates and low complaint rates. Without proper warming, even with a clean list, your emails could land in spam folders or be outright blocked, potentially placing your new domain on a harmful blacklist (or blocklist).
For a list of 6,000 active contacts, this process doesn't need to be overly prolonged, but it certainly shouldn't be rushed. It's about establishing trust. A strategic approach ensures a smooth transition, allowing you to maintain and even improve your inbox placement rates.
Why a new domain needs warming
A new domain, unlike a shared one, has no pre-existing reputation. This is both a challenge and an opportunity. Shared domains come with the risk of other senders' poor practices affecting your deliverability. By moving to a private domain, you gain full control over your sending reputation, which is invaluable for long-term email success. However, this blank slate means you must carefully build your reputation from scratch, earning the trust of ISPs through consistent, positive sending behavior.
ISPs monitor various signals to determine a sender's trustworthiness, including volume, bounce rates, complaint rates, and engagement. Starting with low volumes and gradually increasing them allows ISPs to observe your sending patterns and subscriber engagement. Rushing this process can trigger spam filters, leading to your emails being marked as spam or your domain ending up on a blacklist or blocklist, hindering your ability to reach the inbox.
While a shared domain might initially seem convenient, a dedicated private domain offers significantly more control and less susceptibility to external factors. This move is often prompted by stricter policies from mailbox providers, like recent changes from Google and Yahoo, which emphasize sender authentication and reputation. Taking ownership of your domain's reputation is essential for modern email marketing.
This transition gives you the chance to set a new standard for your email program. It's an opportunity to implement all the best practices from day one, ensuring your private domain becomes a strong asset for your deliverability. Think of it as investing in your future email success.
Shared domain
Pros: Easier initial setup, shared reputation may offer a baseline.
Cons: Vulnerable to other senders' poor practices, less control over reputation.
Impact: Deliverability can fluctuate based on shared IP/domain performance.
Private domain
Pros: Full control over sender reputation, isolated from other senders.
Cons: Requires dedicated warming period to build reputation.
Impact: Stable and predictable deliverability once warmed up.
Developing a strategic warmup schedule
For your 6,000 active contacts, you'll want to start with a very conservative sending volume and gradually increase it. The key is to send to your most engaged subscribers first. This signals to ISPs that your emails are valued and welcomed, establishing positive sending patterns. Your existing open rate of 17-25% indicates a good level of engagement, which is a strong foundation.
A common strategy is to double your sending volume every few days, assuming positive engagement and no issues. Given your 6k contact list, you could potentially complete the core warming within a week or two. Remember that some experts suggest incrementing by 25-30% daily if you have reliable engagement.
Start with a highly engaged segment of your list. These are the contacts who consistently open and click your emails. As you progress, you can broaden your audience to include less engaged, but still active, subscribers. The goal is to consistently generate positive signals.
One key aspect is maintaining consistency. Try to send emails daily, or at least every other day, during the initial warming phase. This helps ISPs build a consistent profile for your new domain. If you skip days, the warming process might take longer as ISPs will need to re-evaluate your sending patterns.
Day
Target volume
Notes
Day 1
250-500
Send to your absolute most engaged segment.
Day 2
500-1,000
Continue with highly engaged contacts.
Day 3
1,000-2,000
Expand to broader active contacts.
Day 4
2,000-4,000
Monitor engagement closely, be ready to adjust.
Day 5
4,000-6,000
If engagement remains strong, send to entire active list.
Optimizing content and engagement for success
During the warming period, the content of your emails is just as important as the volume. You want to send highly engaging, valuable content that encourages opens and clicks. Avoid anything that might trigger spam complaints or low engagement, as these negative signals can quickly derail your warming efforts. Focus on content your audience expects and looks forward to receiving.
Consider sending a welcome series or re-engagement campaign through your old, established domain to inform your contacts about the upcoming domain change. This can help set expectations and encourage them to look for your emails from the new domain, even if they initially land in spam. A heads-up can make a big difference.
Ensure your list is clean and up-to-date. Remove any inactive subscribers, bounces, or known spam traps before you begin sending from the new domain. Sending to a pristine list minimizes negative signals and maximizes positive engagement during this crucial phase. You might also want to review best practices for warming up a domain with a small list as some principles apply regardless of list size.
Focus on high engagement
During warming, prioritize content that reliably gets opens and clicks. This could be exclusive offers, highly anticipated newsletters, or essential updates. The goal is to show ISPs that your recipients actively want your emails.
Monitoring reputation and addressing issues
Constant monitoring is non-negotiable during domain warming. Keep a close eye on your email deliverability metrics. Pay attention to your open rates, click-through rates, bounce rates, and crucially, your complaint rates. Any sudden dips in engagement or spikes in complaints are red flags that require immediate attention. These metrics provide insights into how ISPs and your subscribers are reacting to your new domain.
Regularly check blocklist monitoring tools (also known as blacklist monitoring). Being listed on a major blacklist can severely impact your deliverability. If you find your domain on a blacklist or blocklist, take immediate steps to address the underlying issue, such as cleaning your list, adjusting sending volume, or reviewing content. For a detailed understanding of how these lists work, consider exploring our guide on how email blacklists actually work.
Ensure your domain has proper authentication records configured, including SPF, DKIM, and DMARC. These records verify your identity as a sender and are crucial for building trust with ISPs. Regularly check their status to prevent authentication failures that could harm your new domain's reputation. Our DMARC monitoring can help you keep track of this.
Example DNS records for email authenticationplaintext
Transitioning to a private domain and warming it up for 6,000 active contacts is a manageable but critical process. It's about establishing trust with mailbox providers through consistent, positive sending behavior. By following a structured warming schedule, prioritizing engaging content, and diligently monitoring your performance, you can build a strong sender reputation that ensures your emails reliably reach the inbox.
Remember, a private domain offers long-term benefits in terms of control and deliverability stability. The initial warming investment pays off by providing a reliable foundation for your email marketing efforts, free from the shared domain risks. This strategic move positions you for enhanced email program success and strengthens your overall sender reputation.
Views from the trenches
Best practices
Start with very low volumes, sending to your most engaged subscribers first to establish trust with ISPs.
Gradually increase your sending volume, ideally doubling it every few days, while closely monitoring deliverability.
Ensure all your email authentication records (SPF, DKIM, DMARC) are correctly configured before you start sending.
Use highly engaging content during the warming phase to encourage opens, clicks, and positive interactions.
Common pitfalls
Sending to too many contacts too quickly from a new domain, triggering spam filters and damaging reputation.
Not segmenting your list and sending to inactive or low-engagement contacts during the critical warmup phase.
Neglecting to monitor deliverability metrics, leading to missed opportunities to course-correct.
Failing to pre-warm your audience about the domain change, causing confusion or missed emails.
Expert tips
Expert from Email Geeks says a 6K list can be warmed relatively quickly, potentially within a few days, by starting with very small sends.
Marketer from Email Geeks says they might follow a specific ramp-up: 1K, then 2K, then 4K, then the whole list.
Marketer from Email Geeks says it's beneficial to notify your existing list about the domain change from your old domain.
Expert from Email Geeks says that Microsoft isn’t as strict as Google regarding warm-up speed, potentially allowing for a slightly faster ramp-up.
Marketer view
Marketer from Email Geeks says that 6,000 active contacts are roughly equivalent to day 3 of a typical email warm-up cycle.
2020-05-14 - Email Geeks
Marketer view
Marketer from Email Geeks says that a possible warm-up schedule could involve sending 1K emails, then 2K, then 4K, followed by the entire list.
Microsoft, requires careful planning. A new private domain starts with no prior sending history or reputation, making the warming process critical to avoid deliverability issues.
Gmail and 
Outlook. This involves slowly increasing your sending volume over time, ensuring high engagement rates and low complaint rates. Without proper warming, even with a clean list, your emails could land in spam folders or be outright blocked, potentially placing your new domain on a harmful blacklist (or blocklist).
