Summary
The decision to move promotional email campaigns to a dedicated subdomain is a common one for marketers seeking to protect their sender reputation and improve overall email deliverability. While it offers potential benefits by isolating the reputation of high-volume, lower-engagement sends from critical transactional emails, it also introduces complexities related to warming up new domains and managing separate reputations.
Key findings
- Reputation isolation: Subdomains allow for the separation of different email streams, preventing potential deliverability issues from promotional campaigns from negatively impacting the primary domain used for transactional or higher-priority communications. This is a primary driver for using email subdomains, as highlighted by Mailgun's guide to email subdomains.
- Improved tracking and analytics: Using dedicated subdomains for campaigns can enable more granular tracking and analysis of specific campaign performance, making it easier to identify deliverability issues tied to particular email types.
- Engagement metrics correlation: While lower open and click-through rates on promotional emails might seem alarming, they do not automatically indicate a deliverability problem. Deliverability issues should be confirmed through dedicated inbox testing rather than solely relying on engagement metrics.
- Volume considerations: Splitting email streams requires ensuring sufficient volume for each subdomain, especially for transactional emails. A transactional subdomain might struggle to build a strong reputation if it lacks consistent, high volume sends, which can be protected by other email types on the main domain.
Key considerations
- Assess current deliverability: Before making any changes, confirm if your promotional emails are genuinely experiencing deliverability issues by using inbox testing (e.g., seed lists). A 15-35% open rate typically suggests good inbox placement.
- Reputation dynamics: Understand that separating a struggling email stream onto a new subdomain might worsen its performance rather than protect the main domain. Each subdomain must build its own reputation. Learn more about why you should use subdomains for email marketing.
- Audience segmentation: Evaluate if different email types are targeting the same audience. If not, comparing engagement metrics directly might be misleading, as different audiences naturally interact differently with content.
- Warm-up process: If you create a new subdomain, it will require a careful warming-up process to build its reputation from scratch. This can take time and resources.
- Branding and visibility: Consider the visible impact of using a promotional subdomain (e.g., promo.yourdomain.com) on subscriber perception. While often minor, it's a factor.
What email marketers say
Email marketers often debate the optimal strategy for managing promotional campaigns, particularly when it comes to balancing engagement metrics with overall sender reputation. Many are concerned that lower performance in promotional sends could compromise the deliverability of their more critical email streams, leading them to consider dedicated subdomains.
Key opinions
- Lower OR/CTR concerns: Marketers frequently observe that promotional campaigns tend to have lower open and click-through rates compared to educational or entertainment content. This disparity often prompts questions about potential negative impacts on deliverability and sender reputation. This is why many ask whether they should use a subdomain or main domain for marketing emails.
- Desire for isolated data: A common motivation for separating promotional campaigns to a dedicated subdomain is the ability to gather more precise data points specific to that email type. This can help in identifying and addressing deliverability issues more effectively if they arise.
- Fear of negative impact on domain: There's a prevailing fear that if promotional campaigns perform poorly, they could drag down the overall domain reputation, affecting all email types sent from that domain. Many marketers seek to avoid this by creating a separate sending identity.
- A/B testing interest: Some marketers are inclined to conduct A/B tests with from names on different subdomains to gain clarity on how splitting campaigns impacts engagement and deliverability.
Key considerations
- Reputation dilution risk: While intended to protect, separating a low-engagement stream could isolate it from the positive reputation of higher-performing emails, potentially making deliverability worse for the promotional subdomain, as discussed by Captain Verify.
- Audience consistency: It's important to confirm if the audience receiving promotional emails is the same as for other campaigns. Different audience segments may naturally have different engagement patterns, which could skew perceived deliverability issues.
- Internal resistance: Marketers may face internal opposition to separating campaigns due to concerns about negatively affecting the promotional subdomain's (or primary domain's) reputation and the visible appearance of the sender address.
- Deliverability validation: Relying on open rates alone can be misleading. Marketers should conduct thorough inbox testing using seed lists to accurately determine if emails are landing in the inbox or spam folder. This is a crucial step for diagnosing email deliverability issues.
Marketer view
Marketer from Email Geeks observes that their promotional campaigns have significantly lower open rates, ranging from 15-35%, and click-through rates of 1-3%. They also mention that some promotional campaigns occasionally drop to 10% open rates. These figures are concerning to them, raising doubts about the overall health of their email deliverability.They exclusively mail to subscribers who have engaged with emails within the last three to four months, which should, in theory, lead to higher engagement. This marketer also notes that their other campaign types (educational, entertainment) generally achieve better open and click-through rates, suggesting a disparity in performance across different email streams.
Marketer view
Marketer from Email Geeks indicates that they are just beginning to focus on email deliverability. They have started monitoring their overall IP and domain reputation using tools like Google Postmaster Tools and SNDS, but they have not yet segmented this monitoring by subdomains. They express a desire to start tracking open rates specifically for different domains or subdomains to gain more granular insights into performance.They question if the lower performance of promotional campaigns might be 'evened out' by the stronger performance of other campaign types when judging overall domain health. This suggests an internal debate about whether to maintain a unified sending strategy or to separate streams for clearer analytics.
What the experts say
Email deliverability experts typically offer a nuanced perspective on using dedicated subdomains for promotional campaigns. While acknowledging the theoretical benefits of reputation isolation, they often emphasize the practical implications and potential downsides, particularly concerning the volume of mail and the actual state of deliverability.
Key opinions
- Engagement versus deliverability: Experts often stress that lower open rates do not automatically indicate deliverability issues. They suggest that low engagement might be a content problem rather than a spam filtering problem. A 15-35% open rate is generally considered a strong indicator of emails reaching the inbox.
- Confirmation through testing: Rather than speculating, experts advise concrete inbox testing using seed lists to definitively determine if mail is going to the inbox or spam folder.
- Risk of harming struggling streams: Separating a promotional stream that already has lower engagement could potentially hurt its deliverability further by removing the benefit of shared reputation with higher-performing campaigns. This is a critical consideration when deciding if you should use separate subdomains.
- Volume dependency: The success of a dedicated subdomain relies heavily on sufficient sending volume to maintain a consistent reputation. If transactional volume alone is too low, separating it from promotional volume could inadvertently harm its deliverability.
Key considerations
- Actual deliverability data: Rely on concrete data from deliverability monitoring tools and inbox tests before deciding to move campaigns. Perceived issues based on open rates alone might not justify the complexity of managing additional subdomains.
- Audience consistency: Consider if the same audience receives all email types. If audiences differ, comparing engagement metrics directly between campaign types can be misleading and not indicative of deliverability problems.
- Subdomain warming: A new subdomain requires a proper warm-up period to build reputation, which takes time and consistent sending practices.
- Reputation building: It's crucial to understand how to improve domain reputation using Google Postmaster Tools for each sending identity, whether it's the main domain or a new subdomain.
Expert view
Expert from Email Geeks, in response to lower open and click-through rates, questions the actual numbers for OR/CTR and whether deliverability is being monitored in other ways. They specifically ask if the campaigns are genuinely experiencing worse deliverability. This highlights the importance of data-driven analysis over assumptions based on engagement metrics alone.They also pose a critical question: how much worse would delivery be for lower-performing campaigns if they no longer benefited from sharing reputation with higher-performing campaigns on the same domain? This suggests a caution against prematurely separating email streams without understanding the full impact on overall sender reputation.
Expert view
Expert from Email Geeks asserts that open rates between 15% and 35% generally indicate that mail is successfully reaching the inbox. They challenge the notion that such rates suggest spam delivery issues, prompting the question of what specific indicators lead the marketer to believe their emails are being delivered to spam folders.This opinion underscores a common misconception where lower-than-desired engagement is conflated with deliverability problems, emphasizing the need for proper diagnostic tools and understanding of email performance metrics.
What the documentation says
Technical documentation and industry best practices often advocate for the strategic use of subdomains to manage sender reputation and improve deliverability. They typically highlight the isolation benefits and provide guidelines for implementation, especially when different types of email (e.g., transactional versus promotional) carry different risk profiles or engagement expectations.
Key findings
- Reputation separation: Documentation frequently stresses that subdomains develop their own independent sender reputations. This means that issues like low engagement, high complaint rates, or blocklisting on a promotional subdomain are less likely to impact the primary domain used for critical transactional emails. Mailgun’s documentation on subdomains highlights this benefit.
- Enhanced control: Using subdomains provides greater technical control over different email streams, allowing for distinct SPF, DKIM, and DMARC records tailored to each sending type. This granular control is crucial for authentication and maintaining trust with internet service providers (ISPs).
- Deliverability resilience: By diversifying sending reputations across subdomains, organizations can make their overall email program more resilient. If one subdomain experiences a deliverability setback, it does not necessarily bring down the entire sending infrastructure.
- Categorization and analytics: Subdomains naturally facilitate better categorization of email traffic, which in turn allows for more precise performance monitoring and troubleshooting. This enables easier identification of issues specific to promotional or transactional flows.
Key considerations
- Volume requirements: Each new subdomain requires consistent sending volume to establish and maintain a positive reputation. Low-volume subdomains may struggle to build trust with ISPs, potentially leading to poorer deliverability. This is why it's important to consider if you should use subdomains for promotional and transactional emails.
- Warming up: Any new subdomain needs a careful warm-up process, gradually increasing sending volume to build trust. This is a crucial step that cannot be overlooked.
- Authentication setup: Proper configuration of SPF, DKIM, and DMARC for each subdomain is essential to ensure email authentication and prevent spoofing. Misconfigurations can lead to deliverability issues.
- Complexity: While beneficial, managing multiple subdomains adds a layer of complexity to email infrastructure and monitoring. Organizations need robust systems for DMARC monitoring and blocklist checking for each sending domain.
Technical article
Documentation from Mailgun states that separating promotional emails from transactional ones through the use of new subdomains is a recommended practice. This strategy significantly helps in protecting the primary domain's reputation. They emphasize that different email types often have different recipient engagement patterns, which can affect their sending reputation.By isolating promotional email flows, any issues such as higher complaint rates or lower open rates associated with marketing content will not negatively impact the deliverability of crucial transactional messages, ensuring their consistent arrival in the inbox.
Technical article
Documentation from Medium explains that the negative impacts of email campaigns, such as being marked as spam or experiencing high bounce rates, will only affect the subdomain they are sent from, not the main domain's credibility. This clear separation of reputation is a key advantage of using subdomains.They highlight that this isolation provides a safety net, allowing businesses to undertake more aggressive marketing strategies without jeopardizing the deliverability and sender reputation of their primary domain used for critical communications. It is a fundamental principle for managing risk in email sending.
Related resources
14 resources
Related pages
Why use subdomains for email marketing deliverability?
Should I use separate email subdomains for transactional and promotional emails, and how does engagement affect this?
Should I use a subdomain or my main domain for marketing emails?
What is the best practice for selecting a subdomain for marketing emails and how does it impact deliverability?
Should transactional and marketing emails be sent from separate domains or subdomains?
Email Deliverability Issues: Getting Your Messages to the Inbox in 2025
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How to Improve Domain Reputation Using Google Postmaster Tools [2025 Guide]
A practical guide to understanding your email domain reputation
A simple guide to DMARC, SPF, and DKIM
