Should I use separate IPs or domains for transactional vs marketing emails?
Michael Ko
Co-founder & CEO, Suped
Published 17 Jul 2025
Updated 19 Aug 2025
6 min read
When managing your email sending, a critical question often arises: should you use separate IP addresses or domains for transactional versus marketing emails? It is a question that cuts to the heart of email deliverability. The answer leans heavily towards separation, as mixing these distinct email types can significantly impact your sender reputation and, ultimately, your inbox placement.
Transactional emails, like password resets, order confirmations, or shipping notifications, are typically expected and often eagerly awaited by recipients. They tend to have high open rates and low complaint rates. Marketing emails, on the other hand, are promotional in nature and, while valuable, generally see lower engagement metrics and can sometimes lead to higher spam complaints or unsubscribes.
The core issue is that internet service providers (ISPs) and mailbox providers (MBPs) like Google and Mailgun evaluate sender reputation based on various factors, including engagement and complaint rates. When both types of email share the same sending infrastructure, the lower performance of marketing emails can unfairly drag down the reputation associated with your transactional sends, leading to crucial alerts or confirmations ending up in the spam folder.
Understanding reputation and why separation matters
Understanding how reputation is tracked is key to grasping why separation is so important. Email reputation is not a monolithic score, but rather a complex system that evaluates both IP reputation and domain reputation.
IP reputation is tied to the specific server (or pool of servers) sending your emails. If an IP address is used for high-volume marketing campaigns that generate spam complaints, that IP can get added to an email blacklist or blocklist. This can then affect all emails sent from that IP, regardless of their content, including your critical transactional messages. Conversely, if your IP gets blocklisted, it can severely impact your deliverability across the board.
Domain reputation is linked to your sending domain (e.g., example.com) or subdomain (e.g., mail.example.com). ISPs track how recipients interact with emails from your domain, including opens, clicks, replies, and, most importantly, spam complaints and unsubscribes. A strong domain reputation signals trustworthiness, while a poor one can lead to messages being filtered as spam or rejected entirely. You can read more about understanding your domain reputation here.
By separating your IP addresses and domains (or subdomains), you create distinct reputations for your different email streams. This means that if your marketing efforts hit a snag, say a campaign leads to a spike in complaints, the deliverability of your transactional emails remains largely unaffected because they operate on a separate, high-reputation infrastructure. This segregation is a foundational best practice for maintaining optimal deliverability.
The implementation of separation
When it comes to implementation, you have options for achieving this critical separation. The most common approach involves using separate subdomains and, ideally, separate dedicated IP addresses.
Separate IP addresses for each email type
Using separate IP addresses is often recommended. This means having one dedicated IP address (or pool of IPs) solely for transactional emails and another for marketing emails. This physically separates the sending infrastructure, ensuring that issues on one IP do not cross-contaminate the other. For instance, if your marketing IP gets listed on a DNS-based blacklist, your transactional mail stream (on a different IP) will remain unaffected. Email providers like Outlook often give preferential treatment to IPs with consistent positive sending behavior.
Separate domains or subdomains
Beyond IPs, separating domains or, more commonly, subdomains is crucial. You could use transactional.yourdomain.com for order confirmations and marketing.yourdomain.com for newsletters. This strategy ensures that the reputation built on one subdomain is not directly impacted by the other. It also makes it easier for mailbox providers to categorize your emails and route them appropriately.
Shared IP and single domain
Risk: Your crucial transactional emails could be affected if your marketing emails perform poorly, leading to spam folder delivery or rejection for all emails from that sender. This is because all email types share the same reputation pool.
Monitoring: Difficult, as performance metrics are blended, making it hard to pinpoint issues with a specific email stream.
Separate IPs and subdomains
Benefit: Each email type builds its own reputation. If marketing emails face deliverability challenges, your transactional emails, which are vital for user experience, remain unaffected. This is the gold standard for optimal deliverability.
Monitoring: Streamlined, allowing you to track and address issues specific to each email stream without impacting the other. For more on this, check out our guide on sending from separate domains.
Additionally, ensure proper email authentication (SPF, DKIM, and DMARC) is set up for all your sending domains and subdomains. This validates your emails as legitimate, further boosting their chances of reaching the inbox. You can learn more about these protocols in our simple guide to DMARC, SPF, and DKIM.
Continuous monitoring and authentication
Beyond initial setup, continuous monitoring is non-negotiable. Even with perfect separation, deliverability can fluctuate. Regular checks of your sender reputation, bounce rates, and spam complaint rates for both your transactional and marketing streams are essential. This proactive approach allows you to identify and address issues before they escalate.
Engagement metrics: Monitor open rates, click-through rates, and unsubscribe rates for both streams. Higher engagement generally correlates with better inbox placement.
Complaint rates: Keep a close eye on spam complaint rates. Even a small increase can signal a problem with your list hygiene or content, potentially leading to your IP or domain being put on a blacklist (or blocklist).
Bounce rates: High bounce rates, especially hard bounces, indicate an unhealthy list. Clean your lists regularly to remove invalid or inactive addresses.
While shared IPs can be a good starting point for low-volume senders, the consensus among deliverability experts is that dedicated IPs offer more control over your reputation, especially as your sending volume grows. For more detailed insights into why your emails might be failing, explore our expert guide to email deliverability.
DNS records for subdomains
When setting up separate subdomains, you'll need to configure their DNS records (SPF, DKIM, DMARC) independently. Here's a simplified example of what your DNS entries might look like:
Repeat similar entries for transactional.yourdomain.com, ensuring each subdomain has its own, distinct authentication records. This explicit configuration helps ISPs differentiate and build separate reputations for each sending stream.
Views from the trenches
Best practices
Always separate your transactional and marketing emails to protect the deliverability of critical communications.
Use distinct subdomains like 'transactional.yourdomain.com' and 'marketing.yourdomain.com' for clear segregation.
Implement proper SPF, DKIM, and DMARC authentication for all your sending domains and subdomains.
Regularly monitor engagement metrics, complaint rates, and bounce rates for each email stream independently.
For higher sending volumes, invest in dedicated IP addresses to gain more control over your sender reputation.
Common pitfalls
Sending both transactional and marketing emails from the same IP address or domain, risking deliverability of critical messages.
Neglecting to set up or properly configure email authentication for all subdomains, leading to authentication failures.
Failing to monitor unique metrics for each email stream, making it difficult to pinpoint and address specific issues.
Assuming that good performance of transactional emails will offset poor performance of marketing emails when mixed.
Not cleaning email lists regularly, leading to high bounce rates and potential blacklisting.
Expert tips
For optimal deliverability, consider segmenting your IPs not just by email type (transactional vs. marketing) but also by recipient engagement level within your marketing segments.
Leverage DMARC reports to gain granular insights into how your emails are being authenticated and delivered across different mailbox providers.
When introducing a new IP or subdomain, always follow a warm-up schedule to gradually build a positive sending reputation.
Always ensure that the content and sending practices align with the expectations of the email type being sent (e.g., no promotional content in transactional emails).
Maintain consistent sender identity and branding across all email streams, even with separate sending infrastructure.
Marketer view
Marketer from Email Geeks says IP reputation is tied to the sending system and is often shared across all domains on that IP.
2021-06-26 - Email Geeks
Marketer view
Marketer from Email Geeks says that separating corporate, marketing, and transactional emails into different domains or subdomains is generally recommended, with proper authentication using SPF and DKIM.
2021-06-26 - Email Geeks
Strategic separation for robust deliverability
In the world of email deliverability, the principle of separation for transactional and marketing emails is a cornerstone best practice. By segmenting your sending infrastructure, whether through distinct IP addresses, subdomains, or both, you proactively safeguard the deliverability of your most important messages.
This approach allows each email stream to build and maintain its own sender reputation, preventing the potentially volatile nature of marketing campaigns from negatively impacting the reliability of essential transactional communications. It's an investment in your sender's trustworthiness and the overall health of your email program.
Ultimately, the goal is to maximize the chances of all your emails reaching the intended inbox. Adopting a strategy of separation, combined with diligent monitoring and proper authentication, is one of the most effective ways to achieve and maintain strong email deliverability.
Outlook often give preferential treatment to IPs with consistent positive sending behavior.
