What are the best practices for warming a new domain for marketing emails to existing subscribers?
Michael Ko
Co-founder & CEO, Suped
Published 3 Jun 2025
Updated 24 Sep 2025
6 min read
Launching a new SaaS product on a distinct domain, especially when targeting your existing base of 15,000 opted-in subscribers, presents a unique challenge for email deliverability. While the instinct might be to jump straight into sending marketing emails from the new domain, it's crucial to understand the nuances of domain warming. This isn't just a technical exercise, but also a matter of managing subscriber perception. Sending from an unfamiliar domain, even to engaged subscribers, can trigger spam complaints and negatively impact your sender reputation, making it difficult to reach the inbox consistently.
The core of the issue lies in how inbox providers (like Gmail or Outlook) perceive a new sending domain. They have no prior history of engagement or trust with it. Sending a large volume of emails right away can look suspicious, regardless of the quality of your list. This is why a methodical approach to domain warming is essential to build that trust gradually. It's about establishing a positive sender reputation with these providers, which ultimately dictates whether your emails land in the inbox or the spam folder.
Understanding the impact on recipient perception
One of the most critical aspects of launching a new domain is ensuring your subscribers recognize the sender. Even if they've opted into your core brand, an email arriving from a completely new domain can be confusing. This confusion often leads to higher spam complaint rates, which are detrimental to your sender reputation. A high spam complaint rate signals to email providers that your emails are unwanted, leading to future blocking or throttling.
Consider the user experience: when an email from an unfamiliar domain lands in their inbox, many recipients will instinctively mark it as spam or phishing. This perception can be hard to overcome, even with clear branding within the email itself. The sending domain is a primary identifier, and a sudden change, even with legal consent, can be jarring for a subscriber.
Direct send from new domain
Recipients receive an email from an unrecognized sending domain, potentially leading to confusion and mistrust.
High spam complaints: Subscribers may mark emails as spam due to unfamiliarity, even if they consented.
Damaged sender reputation: High complaint rates severely impact your domain's ability to reach the inbox.
Phased introduction via existing domain
Existing, trusted domain introduces the new brand/product, inviting subscribers to engage with the new domain.
Managed expectations: Subscribers are informed and opt-in to the new communication stream.
Preserved sender reputation: Lowers the risk of complaints and preserves the deliverability of both domains.
Introducing the new domain strategically
Instead of immediately sending from the new domain, a more effective strategy is to leverage your established sender reputation. Use your existing, well-warmed domain to announce the new SaaS product and its associated domain. This pre-introduction allows you to manage subscriber expectations and gain their explicit or implicit consent to receive communications from the new domain.
For example, send an email from your-old-domain.com introducing your-new-saas-domain.com. Within this email, you can invite subscribers to click a link to learn more, sign up for updates from the new product, or explicitly confirm they wish to receive emails from the new domain. This 'double opt-in' style interaction provides a clear signal of engagement to email providers and reduces the risk of complaints. It's a key part of how to warm up a new domain effectively, especially for a large list.
Key considerations for introducing a new domain
Clear communication: Clearly state in your existing brand's email that a new domain will be used for product-specific communications.
Consent reinforcement: Offer a clear call to action to confirm their interest in receiving emails from the new domain.
Branding consistency: Maintain consistent branding between the introduction email and the first emails from the new domain.
Gradual volume increases and email authentication
Once you've successfully introduced your new domain to your existing subscribers and gained their re-engagement, you can begin the technical process of gradually warming it up. This involves slowly increasing your sending volume over several days or weeks. The goal is to send enough emails to establish a sending pattern without overwhelming inbox providers and triggering their spam filters. You're trying to build a positive domain reputation from the ground up.
Even though you're on a shared IP with HubSpot, the domain's reputation is distinct. You need to ensure proper email authentication is in place from day one. This includes SPF, DKIM, and critically, a DMARC record. DMARC will provide valuable feedback through aggregate reports on how your emails are authenticating, which is essential for guiding your warm-up process.
A DMARC monitoring tool like Suped is invaluable during this phase, offering clear insights into your email authentication status and deliverability. It will show you exactly how many emails are passing or failing SPF/DKIM and what actions are being taken by recipients, allowing you to make data-driven adjustments.
Monitoring deliverability and adapting your strategy
During the warm-up period, vigilant monitoring of your email metrics is paramount. Pay close attention to engagement rates (opens, clicks), bounce rates, and especially spam complaint rates. If you see an increase in complaints or bounces, it's a sign to slow down your sending volume and investigate the cause. Tools like Google Postmaster Tools can provide valuable data specific to Gmail recipients, offering insights into your domain's reputation and deliverability performance.
Additionally, blocklist monitoring is essential. If your new domain (or the associated IP) ends up on a major blacklist (or blocklist), it can severely hamper your sending efforts. Regularly check to ensure your domain remains clean. If you find yourself on a blocklist, promptly address the issue and request delisting.
Day
Volume (emails)
Key action
1-3
500-1,000
Highly engaged segment, confirm opt-in.
4-7
1,000-2,000
Gradually expand to a slightly less engaged segment.
Always introduce your new brand or product domain using your well-established, known sending domain first.
Ask subscribers to explicitly confirm their interest in receiving communications from the new domain.
Segment your most engaged subscribers for the initial sends from the new domain to build positive engagement.
Implement and monitor DMARC, SPF, and DKIM from the very beginning to ensure authentication.
Common pitfalls
Sending emails from a new, unrecognized domain directly to existing subscribers without prior introduction.
Ignoring early spam complaints or bounce rates, which can quickly lead to blocklisting.
Not having a DMARC policy in place, which means you lack visibility into authentication issues.
Trying to send a large volume of emails too quickly from a completely new domain.
Expert tips
Use your existing domain to educate your audience about the new brand and its distinct email sending domain.
Leverage initial emails from the new domain to drive engagement and reinforce brand recognition.
Monitor your domain's reputation with tools like Google Postmaster Tools and a DMARC monitoring solution.
Be prepared to slow down sending if negative feedback or deliverability issues arise during warming.
Marketer view
Marketer from Email Geeks says that recipients need to understand why they are getting an email from a new brand or product domain, otherwise it risks being marked as spam.
September 15, 2025 - Email Geeks
Marketer view
Marketer from Email Geeks says that if people don't know they opted in for the new brand's emails, they are highly likely to report it as spam, noting that even 45 complaints can be too many for 15,000 recipients.
September 15, 2025 - Email Geeks
Achieving deliverability with a new domain
Successfully warming a new domain for marketing emails to existing subscribers requires a two-pronged approach. First, prioritize your subscribers' perception by using your established domain to introduce the new product and its associated sending domain. This crucial step helps mitigate potential spam complaints and sets a positive tone. Second, meticulously follow a gradual volume increase strategy, ensuring all email authentication protocols (SPF, DKIM, DMARC) are correctly configured and actively monitored.
By combining strategic communication with technical diligence and continuous monitoring, you can build a strong sender reputation for your new domain, ensuring your marketing messages reach the inboxes of your valued subscribers. Remember, patience and attention to detail are key to long-term email deliverability success.
Gmail or 
Outlook) perceive a new sending domain. They have no prior history of engagement or trust with it. Sending a large volume of emails right away can look suspicious, regardless of the quality of your list. This is why a methodical approach to domain warming is essential to build that trust gradually. It's about establishing a positive sender reputation with these providers, which ultimately dictates whether your emails land in the inbox or the spam folder.
