What is the best practice for warming up a new email sending domain for a small list of cold contacts?
Matthew Whittaker
Co-founder & CTO, Suped
Published 11 Jun 2025
Updated 30 Sep 2025
7 min read
Warming up a new email sending domain, especially when targeting a list of cold contacts, can feel like navigating a minefield. The goal is to build a positive sender reputation with internet service providers (ISPs) so your emails land in the inbox, not the spam folder. This process requires patience and a strategic approach, as rushing can lead to immediate blacklisting and significant deliverability issues.
The challenge is amplified when dealing with contacts who haven't actively engaged with your brand recently. ISPs meticulously track engagement metrics like open rates, click-through rates, and complaint rates. A sudden influx of emails from a new domain, particularly to disengaged recipients, signals suspicious activity, which can quickly harm your sender reputation.
However, with a well-planned warm-up strategy, even a small list of cold contacts can be approached safely. The key lies in gradual volume increases, meticulous monitoring, and ensuring your foundational email authentication is rock solid. We'll explore the best practices to help you establish trust and achieve excellent deliverability from day one.
Setting the foundation for success
Before you even think about sending your first email, several foundational steps are critical for building a trustworthy sending environment. The age of your domain plays a role, as newly registered domains are often viewed with suspicion by ISPs. Ideally, your domain should be at least 30 to 90 days old, with a functioning website in place, even if it's just a simple redirect to your main site. This helps establish legitimacy in the eyes of postmasters and automated systems.
Setting up robust email authentication is non-negotiable. This includes SPF, DKIM, and DMARC. These protocols verify that your emails are legitimate and prevent spoofing, significantly boosting your sender reputation. A properly configured DMARC record, for instance, provides instructions to receiving servers on how to handle emails that fail authentication checks. Tools like the free DMARC record generator can assist in creating the correct records.
Lastly, for cold lists, list hygiene is paramount. Even if contacts consented at an event, they might not remember you or be eager to receive an email. Clean your list thoroughly to remove any invalid or old addresses. Sending to known spam traps or inactive users will immediately damage your reputation, making the warm-up process much harder. Consider if email warmup is necessary for sending cold emails.
Handling cold contacts on a new domain
For lists gathered over time, especially from events, explicit reminders of consent are crucial. Clearly state how and when you collected their email address in your initial communication. This transparency helps reduce spam complaints and improves the likelihood of engagement, which is vital for a new domain's reputation. Don't assume they remember you.
The gradual warm-up strategy
The core of domain warming involves gradually increasing your sending volume to build trust with ISPs. For a small list of 1,000 cold contacts, a very conservative approach is best. Start with extremely small batches. For example, some experts suggest beginning with as few as 10 emails, waiting a few hours, and then repeating this a few times on the first day. This gentle introduction allows ISPs to see consistent, low-volume sending activity.
The gradual increase is key. Double your batch size each subsequent day, or increase it by a manageable percentage. The exact schedule can vary, but generally, it takes 3-6 weeks to warm up a domain sufficiently. Pay attention to how different recipient domains (like Gmail, Outlook, Yahoo) respond, as some are more sensitive than others. Batching emails per recipient domain can also be beneficial during this phase. This nuanced approach aligns with best practices for domain warm-up.
Day
Daily Volume
Notes
Day 1
10-25
Send in small batches (e.g., 5-10 emails) spread throughout the day.
Days 2-3
25-50
Monitor engagement closely, look for opens and clicks.
Days 4-7
50-100
Increase volume if engagement is healthy and no issues arise.
Week 2-3
100-300
Continue gradual increases, spreading sends throughout the day.
Week 4+
300+
Scale up as reputation stabilizes, always prioritizing engagement.
Focus on highly engaged segments of your list first, if possible. Even with a cold list, some contacts might be more responsive than others. Prioritize sending to those who have recently interacted with your brand or showed the highest interest. Avoid sending to your entire list at once, and never blast the list, especially early on. Remember, the goal is to show ISPs that your emails are valued by recipients.
Monitoring and adaptation
Constant monitoring is non-negotiable during the warm-up period. Keep a close eye on your sending metrics, including open rates, click-through rates, bounce rates, and crucially, complaint rates. Low engagement or high complaint rates are red flags that necessitate slowing down or adjusting your strategy. Aim for an open rate greater than 20% and minimal spam complaints. If you notice any dips in deliverability, pause your sending and reassess.
Regularly check email blocklists (or blacklists) to ensure your new domain hasn't been listed, which can happen if your emails trigger spam filters. Tools like Suped's blocklist monitoring can provide real-time alerts. Additionally, DMARC monitoring is essential for understanding authentication failures and gaining insights into how ISPs are treating your emails. This visibility is key to a successful warm-up for a new domain with a small list.
Risky sending practices
Rapid volume increases: Sending too many emails too quickly from a new domain.
Ignoring metrics: Failing to monitor bounces, complaints, and engagement rates.
No list cleaning: Sending to old or unverified contacts, increasing spam trap hits.
Safe sending practices
Gradual scaling: Slowly increasing volume over several weeks, especially to new email domains.
Proactive monitoring: Checking deliverability tests and sender reputation tools regularly.
Segmented sending: Targeting your most engaged contacts first.
If you hit any snags, such as a sudden drop in inbox placement or an increase in bounce rates, investigate immediately. This could indicate a problem with your content, list, or sending practices. It might mean slowing down your warm-up or even pausing to troubleshoot. Continuous vigilance helps prevent emails from going to spam.
Content and recipient engagement
The content of your warm-up emails is just as important as the sending schedule, especially for cold contacts. Your initial emails should be highly relevant, clearly state how the recipient's information was obtained (e.g., from an event booth), and offer immediate value. A simple statement email, as mentioned in the original query, could work, but ensure it's easy to understand and provides clear next steps. Avoid overly promotional language in these early stages.
Since these contacts are 'cold,' manage your expectations for engagement. While high open and click rates are ideal, a lower initial response is to be expected. The goal here is to establish a baseline of positive interaction, not to achieve peak performance immediately. Encourage replies or simple clicks to demonstrate engagement to ISPs. Even a few positive interactions can significantly contribute to building your domain's reputation.
Finally, remember that the warm-up is not a one-time event. Email lists can go cold again if left unused for too long, necessitating another warm-up period. Continuously maintain good list hygiene, regularly remove inactive subscribers, and send consistent, valuable content to foster ongoing engagement. This proactive approach ensures your domain reputation remains strong.
Concluding thoughts on warming up
Warming up a new email sending domain for a small list of cold contacts requires a methodical and patient approach. By focusing on foundational authentication, implementing a gradual sending schedule, crafting transparent and engaging content, and diligently monitoring your metrics, you can successfully build a strong sender reputation. Remember, consistency and positive recipient interaction are your best allies in ensuring your emails consistently reach the inbox.
Views from the trenches
Best practices
Ensure your domain is at least 30-90 days old and has a live website before sending.
Start with very small sending volumes, like 10-25 emails, and gradually increase over weeks.
Clearly state how consent was obtained in your first emails to cold contacts.
Implement SPF, DKIM, and DMARC for robust email authentication.
Common pitfalls
Sending to a brand new domain that lacks established history and a website.
Increasing email volume too quickly, triggering spam filters and blocklists.
Ignoring engagement metrics such as open rates, click-throughs, and complaints.
Not cleaning your list, which can lead to hitting spam traps and high bounce rates.
Expert tips
Always prioritize high engagement and low complaint rates during the warm-up period.
Utilize DMARC reporting tools like Suped to gain visibility into your email authentication status.
Consider segmenting your list to send to the most responsive contacts first.
If deliverability drops, reduce sending volume immediately and investigate the cause.
Marketer view
Marketer from Email Geeks says that for sensitive ISPs like Gmail, starting with small batches of 10 emails, waiting a few hours, and then repeating is a good initial strategy. The volume can then be doubled each day.
February 12, 2020 - Email Geeks
Expert view
Expert from Email Geeks says that ensuring the domain is not brand new is crucial. Putting up a website, even a simple redirect to the main site, helps establish credibility.
The core of domain warming involves gradually increasing your sending volume to build trust with ISPs. For a small list of 1,000 cold contacts, a very conservative approach is best. Start with extremely small batches. For example, some experts suggest beginning with as few as 10 emails, waiting a few hours, and then repeating this a few times on the first day. This gentle introduction allows ISPs to see consistent, low-volume sending activity.
