Can I use two subdomains on one dedicated IP address for different email types?
Michael Ko
Co-founder & CEO, Suped
Published 1 Jun 2025
Updated 19 Aug 2025
8 min read
Many email senders find themselves wondering if it's possible to use two different subdomains on a single dedicated IP address for various email streams, like transactional messages and marketing campaigns. It's a common question, especially when trying to optimize email deliverability and reputation without incurring extra infrastructure costs for additional IPs. I can tell you that the answer is yes, it is generally possible, but there are important considerations to keep in mind regarding how mailbox providers interpret your sending behavior.
The core idea behind using subdomains is to segment your email sending. By separating different email types onto distinct subdomains, you can theoretically isolate their sender reputations. For instance, if your marketing emails occasionally trigger spam complaints, using a separate subdomain for them might help protect the deliverability of your critical transactional emails. However, when these subdomains share the same dedicated IP, the nuances become a bit more complex.
Mailbox providers are sophisticated, and they look at multiple signals beyond just the IP address or the main domain to assess sender reputation. While a dedicated IP gives you exclusive control over its reputation, the subdomains you use still contribute significantly to how your mail is perceived. Understanding this interaction is key to maintaining strong deliverability rates.
Understanding reputation segmentation
When you use two subdomains on a single dedicated IP, the IP's reputation is influenced by the aggregate sending behavior across both subdomains. Think of the dedicated IP as the shared highway, and the subdomains as separate lanes for different types of traffic. While the lanes are distinct, major issues on one lane can still cause congestion for the entire highway. This means that if one subdomain experiences a significant drop in engagement or a surge in spam complaints, it can negatively impact the deliverability of emails sent from the other subdomain, even if their content is well-received.
However, it's not all doom and gloom. Each subdomain develops its own reputation in the eyes of internet service providers and mailbox providers. This segmentation allows you to manage and monitor the performance of each email stream independently. For instance, you might notice higher bounce rates or lower open rates for your promotional emails sent via marketing.yourdomain.com, while your transactional emails from transactional.yourdomain.com remain stellar. This granular insight is invaluable for targeted optimization. You can learn more about how using a subdomain affects your primary domain's reputation.
The key is to remember that while the subdomains offer a layer of separation, the underlying dedicated IP is still a fundamental factor in deliverability. Mailbox providers like Google and Yahoo have advanced algorithms that can discern different mail streams even if they originate from the same IP address. They analyze content, sending patterns, engagement metrics, and various authentication signals to build a comprehensive reputation profile for each sender, regardless of how many subdomains are used on a single IP.
Technical setup and DNS considerations
Setting up your DNS records correctly is crucial when using multiple subdomains on one dedicated IP for email. You'll need to ensure proper SPF, DKIM, and DMARC records are in place for each subdomain. While the SPF record typically points to your sending IP, the DKIM signatures are tied to the domain (or subdomain) you are sending from. This allows mailbox providers to verify that the email truly originated from your authorized sender.
For optimal separation, it's beneficial if your email service provider (ESP) allows you to use different DKIM domain (d=) values for each subdomain, even if they share the same IP. This further signals to mailbox providers that these are distinct sending entities. Here's a simplified example of how DNS records might look for two subdomains sharing an IP:
Notice how both SPF records point to the same sender, but the DKIM records are distinct for each subdomain, reinforcing their individual identities. This kind of configuration is what allows mailbox providers to differentiate your email streams effectively. When you use separate subdomains for marketing and transactional emails, even on a shared IP, it signals to ISPs that you are taking steps to manage your sending responsibly.
Advantages and disadvantages
While using two subdomains on one dedicated IP is feasible, it comes with a mix of advantages and potential drawbacks. Understanding these can help you make an informed decision for your email strategy.
Advantages
Reputation segmentation: Helps isolate the reputation of different email streams, especially if one type of email (e.g., marketing) has higher risk.
Cost efficiency: Avoids the need for multiple dedicated IPs, which can be costly and require sufficient sending volume to warm up and maintain. This is beneficial if you only have one dedicated IP.
Simplified management: You only manage one IP's overall health and blocklist status (though subdomains can still be blocklisted).
Clear analytics: Easier to track performance metrics for each email type, allowing for more targeted content and audience adjustments.
Disadvantages
Shared IP risk: While subdomains offer some isolation, a severe blocklist event on the IP (e.g., from spam traps) would impact all sending from that IP.
Interdependent reputations: Poor performance on one subdomain can still bleed into the other, as mailbox providers can still link them back to the same IP. For more information, read this article on email subdomains.
Complex setup: Requires careful DNS configuration for each subdomain, including SPF, DKIM, and DMARC.
Monitoring effort: You need to monitor the reputation of each subdomain and the shared IP, which adds a layer of complexity to your deliverability efforts.
Ultimately, the decision to use two subdomains on one dedicated IP often comes down to balancing the desire for reputation segmentation with the practicalities of managing IPs and sending volumes. For some, it's a perfectly viable strategy, particularly if acquiring an additional dedicated IP isn't an option. For others, particularly high-volume senders with vastly different email types, separate IPs might still be the optimal choice to truly isolate sending reputations and minimize risk.
Best practices for shared IP and multiple subdomains
To maximize your email deliverability when using multiple subdomains on a single dedicated IP, consider the following best practices:
Consistent sending behavior: Maintain consistent sending volumes and patterns for each subdomain. Erratic sending can trigger spam filters.
Monitor engagement: Keep a close eye on open rates, click-through rates, and, crucially, spam complaint rates for both subdomains. Low engagement or high complaints on one can affect the other and the shared IP's standing.
List hygiene: Regularly clean your mailing lists to remove inactive or invalid email addresses. This reduces bounces and the risk of hitting spam traps.
Authentication standards: Ensure all your DNS authentication records (SPF, DKIM, DMARC) are correctly configured and aligned for both subdomains. This is a foundational step for email security and deliverability. You can refer to this article for more information on email sending IPs and domains.
Content quality: Maintain high-quality, relevant content for all your email types. Poor content can lead to user complaints and negatively affect your sender score.
While having separate IPs for different email streams offers the highest degree of reputation isolation, using multiple subdomains on a single dedicated IP is a practical and often effective alternative, especially for senders who might not have the volume to justify multiple dedicated IPs. It allows for a degree of reputation segmentation while simplifying IP management. The key is vigilant monitoring and adherence to best practices for both your subdomains and the shared dedicated IP.
Views from the trenches
Best practices
Always align your DMARC records with your subdomain structure, ensuring authentication passes for each sender.
Segment your audience precisely for each subdomain to ensure content relevancy and maintain high engagement.
Regularly monitor deliverability metrics for each subdomain to quickly identify and address any performance issues.
Implement feedback loops for all subdomains to capture spam complaints directly from mailbox providers.
Start with lower sending volumes on new subdomains to build a positive reputation gradually.
Common pitfalls
Assuming complete reputation isolation: while subdomains help, the underlying IP's reputation still plays a significant role.
Neglecting one subdomain's performance: poor engagement on one can negatively affect others on the same IP.
Improper DNS setup: incorrect SPF, DKIM, or DMARC records can lead to authentication failures and deliverability issues.
Inconsistent content or sending patterns: this can confuse mailbox providers and trigger spam filters.
Not monitoring blocklists (blacklists) for the shared IP and individual subdomains regularly.
Expert tips
Utilize subdomains to categorize your email types, such as transactional, promotional, and notification, even when using one IP.
Ensure your email service provider allows for distinct DKIM signatures for each subdomain, as this strengthens reputation signals.
Focus on maintaining excellent list hygiene across all sending streams to prevent hitting spam traps or generating complaints.
Leverage DMARC reports to gain insights into how each subdomain is performing in terms of authentication and delivery.
Consider the combined volume and nature of your emails when deciding if a single dedicated IP is sufficient for multiple subdomains.
Expert view
Expert from Email Geeks says that using two subdomains on one dedicated IP is acceptable. The reputation of each mail type can impact the other, but each subdomain will also have its own reputation. This setup is similar to a shared IP where multiple domains send from the same IP, but in this case, both domains are from the same entity. This can be beneficial for senders who don't have enough volume to justify separate IPs for each email stream but have sufficient combined traffic.
2023-06-27 - Email Geeks
Expert view
Expert from Email Geeks says that to ensure mail streams are treated somewhat separately, it is advisable to use different 'd=' values in the DKIM signatures. Checking if your automation does this by default is worthwhile.
2023-06-28 - Email Geeks
Key takeaways for optimal deliverability
In conclusion, using two subdomains on a single dedicated IP address for different email types is a viable strategy that many organizations employ. It allows for a degree of reputation segregation between transactional and marketing emails, helping to protect your most critical communications from the potential pitfalls of bulk sending. However, it's not a complete firewall. The shared dedicated IP means that a significant negative impact on one subdomain's reputation can still ripple through and affect the other.
Effective implementation hinges on meticulous DNS configuration, consistent sending practices, and continuous monitoring of your email deliverability metrics. By diligently managing each subdomain's sender reputation and adhering to email best practices, you can successfully leverage this setup to maintain strong inbox placement for all your email streams.
Google and 
Yahoo have advanced algorithms that can discern different mail streams even if they originate from the same IP address. They analyze content, sending patterns, engagement metrics, and various authentication signals to build a comprehensive reputation profile for each sender, regardless of how many subdomains are used on a single IP.
