Is DMARC essential for email deliverability and what to do when Return Path reports spam issues with good open rates?
Michael Ko
Co-founder & CEO, Suped
Published 26 May 2025
Updated 19 Aug 2025
7 min read
Email deliverability can feel like a labyrinth, especially when different data sources tell conflicting stories. I often encounter situations where a sender is diligently monitoring their performance, only to find seemingly contradictory reports. One common scenario that raises eyebrows is when a platform like Return Path indicates a high spam placement, yet the internal metrics show robust open rates.
This discrepancy begs the question: Is DMARC truly essential for email deliverability, and what should be done when a prominent deliverability reporting service flags spam issues despite seemingly healthy engagement? Let's dive into these complexities and unpack what's really happening.
DMARC, or Domain-based Message Authentication, Reporting, and Conformance, is an email authentication protocol that builds upon SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). While SPF verifies the sender’s IP address and DKIM uses a cryptographic signature to validate the message content, DMARC provides a policy layer. It instructs receiving mail servers on how to handle emails that fail SPF or DKIM authentication, offering options like monitoring, quarantining, or rejecting messages. This framework helps prevent email spoofing and phishing attempts, protecting your domain's reputation.
For years, DMARC was seen as a best practice, a strong recommendation for advanced email security. However, its status has rapidly evolved. With new sender requirements rolled out by major mailbox providers, particularly Google and Yahoo in 2024, DMARC has become unequivocally essential for bulk senders. Failure to implement DMARC, along with properly configured SPF and DKIM, can lead to significant deliverability issues, including emails being marked as spam or outright rejected. This means that if you're sending a substantial volume of emails, having a DMARC policy in place is no longer optional; it's a fundamental requirement for reaching the inbox.
Why DMARC is crucial
Implementing DMARC provides significant benefits beyond just meeting new sender requirements. It gives you control over your email domain, protecting against unauthorized use and providing valuable insights into your email stream. For a more detailed understanding of its components, you can refer to a simple guide to DMARC, SPF, and DKIM. The benefits extend to protecting your brand and improving trust with mailbox providers.
One of the most powerful aspects of DMARC, even with a basic policy like p=none, is the reporting mechanism. DMARC reports (RUA and RUF) offer aggregated and forensic data on email authentication results across the internet. These reports provide invaluable visibility, allowing you to see how your emails are being authenticated, detect any unauthorized sending from your domain, and troubleshoot issues like SPF or DKIM failures. This insight is critical for maintaining a healthy email program.
Decoding Return Path reports and open rates
This is a common source of confusion. A service like Return Path (now Validity) uses a network of 'seed' email addresses placed across various mailbox providers to test where your emails land. When Return Path reports 100% spam placement, it means all the emails sent to their seed addresses landed in the spam folder, not the inbox. However, your own metrics showing a 20% open rate for Gmail tell a different story for your actual subscribers. This suggests that your engaged subscribers are indeed receiving and opening your emails.
Seedlist results
Seedlist providers use a set of email addresses to simulate inbox placement across various ISPs. A 100% spam report means emails sent to these specific addresses consistently land in the spam folder. These addresses typically don't engage with your emails, so they reflect a raw, unfiltered assessment of your sender reputation from the perspective of the mailbox provider's filters.
Real-world engagement
Your internal open rates, especially from actively engaged segments, indicate that a significant portion of your actual subscribers are receiving your emails in their primary inbox. This is because engaged users develop a positive reputation with their specific mailbox providers, often overriding general filters. Their actions (opening, clicking, replying) signal to the Gmail algorithm that your messages are desired.
The core issue here is that seedlist results act as an early warning signal about your broader sender reputation, particularly for unengaged or new recipients. While your active subscribers might pull your emails into the inbox, others who aren't as engaged or who are receiving your mail for the first time might experience the spam folder placement reported by the seedlist. This is a concerning sign that could impact your long-term deliverability if not addressed.
While DMARC provides a critical authentication layer, it's important to remember that email deliverability is a multi-faceted challenge. Authentication is foundational, but it doesn't guarantee inbox placement on its own. Your sender reputation, content quality, list hygiene, and subscriber engagement all play equally vital roles. A strong reputation, built on consistent positive engagement and low complaint rates, is paramount. If you're encountering issues, it's worth reviewing your overall email deliverability strategy, not just DMARC.
Best practices for deliverability
List hygiene: Regularly clean your email list by removing inactive subscribers, hard bounces, and known spam traps. A smaller, engaged list outperforms a large, dormant one.
Engagement focus: Prioritize sending to your most engaged segments. High open and click rates signal positive intent to ISPs.
Content quality: Avoid spam trigger words, broken links, and overly image-heavy designs. Ensure your emails are relevant and provide value.
Consent management: Only send to recipients who have explicitly opted in. This reduces spam complaints and improves reputation.
Another crucial aspect, especially when switching email service providers (ESPs) or starting with a new IP, is IP warming. Mailbox providers need time to build a reputation for new sending IPs. During this period, it's common for emails to initially land in the spam folder or promotional tabs. A gradual increase in sending volume, coupled with high engagement, helps build a positive reputation over time. This warming process is a critical step to ensure your emails reliably reach the inbox in the long run.
Troubleshooting spam issues with good open rates
If Return Path or similar services consistently report spam issues, even with good open rates, it's a signal you shouldn't ignore. The good open rates show that your highly engaged audience is pulling your emails into the inbox. However, the seedlist results indicate that your general domain and IP reputation might be weaker than you perceive, especially for recipients who aren't already highly engaged. This could lead to emails landing in spam for new subscribers, or those who rarely open your mail, negatively impacting your long-term sender health.
When analyzing performance, I recommend focusing on trends in raw numbers rather than just rates, especially if your audience size changes. For instance, if you cut your audience in half but maintain similar raw open numbers, it means your engagement rate has indeed doubled, but the total number of people receiving your mail might have decreased significantly. This signals that you've effectively pruned your unengaged list, but it doesn't necessarily mean your overall inbox placement has improved for all potential recipients. You can gain further insights into this by checking your domain reputation in Google Postmaster Tools.
Metric
Previous sending (Example)
New sending (Example)
Delivered emails
127,817 - 131,415
48,961 - 72,933
Opened emails (raw)
11,269 - 13,555
11,286 - 12,759
Open rate
8-10%
20-30%
This data clearly illustrates that while your rates improved by segmenting to engaged users, your raw open volume remained similar despite a significantly smaller audience. This points to a healthy core audience, but it also highlights that a large portion of your previous list was likely not engaging or, more critically, having their emails delivered to the spam folder. Addressing the underlying reputation issue will be key to expanding your reach while maintaining high engagement.
Views from the trenches
Best practices
Always implement DMARC, SPF, and DKIM for domain authentication to build trust.
Focus on sending to engaged subscribers to improve overall sender reputation.
Regularly monitor DMARC reports for authentication failures and unauthorized sending.
Segment your audience to prioritize sending to those most likely to engage.
Understand that seedlist results indicate general reputation, while internal metrics show engaged user placement.
Common pitfalls
Assuming DMARC is not essential for deliverability because SPF and DKIM are present.
Ignoring seedlist spam reports due to good internal open rates, missing early warning signs.
Not monitoring raw open numbers alongside open rates when list segmentation changes.
Neglecting IP warming when moving to a new sending platform or IP address.
Failing to clean unengaged users or spam traps from your subscriber lists.
Expert tips
DMARC gives you control over your email domain and protects against impersonation.
DMARC reports provide insight into authentication problems and potential phishing.
IP warming means it's normal for emails to land in bulk/spam initially.
Mailbox providers don’t calculate open rates the same way marketers do.
Prioritize monitoring Gmail deliverability as it often indicates overall trends.
Marketer view
Marketer from Email Geeks says DMARC's necessity depends on the specific goals, but it functions primarily as a policy to define actions when SPF and DKIM fail.
2020-01-28 - Email Geeks
Expert view
Expert from Email Geeks says DMARC is not a direct necessity for email delivery itself; however, it is a highly recommended best practice. Missing DKIM on the From header or SPF on the Return-Path header might cause bounces, while a missing DMARC record will not cause those kinds of immediate delivery problems.
2020-01-28 - Email Geeks
Sustaining your email health
In conclusion, DMARC is no longer just a recommended best practice for email deliverability; it's rapidly becoming a foundational requirement, especially for senders with significant email volume. Its role in protecting your domain from spoofing and providing crucial authentication insights is indispensable. While a 100% spam report from a seedlist monitoring service can be alarming, it needs to be interpreted in context with your actual engagement metrics. Good open rates from engaged subscribers suggest your emails are indeed reaching many inboxes, but the seedlist report acts as a vital early warning system for your broader reputation, particularly for unengaged segments and new sign-ups.
The key is to proactively address potential reputation issues by refining your sending practices, maintaining strict list hygiene, and continuously monitoring all available deliverability signals. By focusing on both technical authentication and strong engagement, you can navigate the complexities of email deliverability and ensure your messages consistently land in the inbox.
Gmail algorithm that your messages are desired.
