How do DMARC, spam complaints, and IP reputation affect email deliverability and rejections?
Matthew Whittaker
Co-founder & CTO, Suped
Published 3 Aug 2025
Updated 16 Aug 2025
7 min read
Email deliverability can feel like a complex puzzle, with many pieces influencing whether your messages land in the inbox or end up in the spam folder (or worse, get rejected entirely). Among the most critical pieces are DMARC, spam complaints, and your IP reputation. These factors aren't isolated, but rather interconnected, collectively shaping how mailbox providers view your sending practices and trustworthiness.
Understanding how each of these elements works, and more importantly, how they interact, is crucial for anyone serious about optimizing their email marketing efforts and ensuring consistent inbox placement. A strong understanding can help prevent common pitfalls that lead to messages being blocked or flagged as unsolicited, safeguarding your sender reputation.
DMARC, or Domain-based Message Authentication, Reporting, and Conformance, is an email authentication protocol that builds upon SPF and DKIM. Its primary purpose is to help domain owners protect their domain from unauthorized use, such as email spoofing and phishing attacks. By implementing a DMARC record, you instruct receiving mail servers on how to handle emails that fail authentication protocols.
The DMARC policy you choose has a direct impact on email deliverability and rejections. A `p=none` policy, while useful for initial monitoring, tells receiving servers not to take any action if authentication fails. However, a `p=quarantine` policy suggests placing failed emails in the spam folder, and a `p=reject` policy instructs servers to block them entirely. If legitimate emails fail authentication under a reject policy, they simply won't be delivered, leading to email rejections. This is why it's crucial to troubleshoot DMARC failures diligently.
While having DMARC set up correctly, including the `rua` (reporting URI for aggregate reports) tag, is vital for gaining visibility into your email flows and detecting unauthorized sending, the `rua` tag itself does not directly influence deliverability. It's a monitoring mechanism that helps you monitor email spoofing and legitimate authentication issues. For example, issues with DMARC impact on Gmail can be identified through these reports.
Setting up DMARC for optimal deliverability
Implementing DMARC provides crucial insights into your email ecosystem. By starting with a `p=none` policy, you can gather aggregate reports and forensic data without affecting email delivery. This allows you to identify all legitimate sending sources and ensure they are properly authenticated before moving to stricter policies like `quarantine` or `reject`.
The direct link between spam complaints and reputation
Spam complaints are one of the most damaging signals to your sender reputation. When a recipient marks your email as spam, it tells their mailbox provider that your content is unsolicited or unwelcome. A high number of these complaints can quickly degrade your reputation, regardless of your DMARC setup.
While DMARC rejections are due to authentication failures, high spam complaint rates directly affect your inbox placement. Mailbox providers, like Gmail and Yahoo, are very sensitive to user feedback. If recipients consistently mark your emails as spam, your overall domain reputation will plummet. This then leads to emails being routed directly to the spam folder, or in severe cases, outright blocking (being added to a blocklist).
It's important to distinguish between DMARC rejections and rejections due to spam complaints. A DMARC rejection means the email failed authentication and the DMARC policy instructed the receiving server to reject it. A spam complaint, on the other hand, signals a content or list quality issue. While a high spam rate may eventually contribute to a poor IP reputation and subsequent junking, it typically won't cause a DMARC-specific rejection. Mailbox providers like Gmail rarely reject emails for spam reasons alone, preferring to filter them to junk.
Good practices
List hygiene: Regularly clean your email lists to remove inactive or invalid addresses, reducing bounces and complaints.
Relevant content: Send emails that recipients genuinely find valuable and have opted to receive.
Clear unsubscribe: Make it easy for subscribers to opt out, reducing their need to mark as spam.
Common pitfalls
Purchased lists: Sending to bought or rented lists is a surefire way to accumulate spam complaints.
Irrelevant content: Sending emails that don't match subscriber expectations or interests.
Lack of engagement: Low open and click-through rates can indirectly lead to higher spam flags.
IP reputation and domain reputation in detail
Your IP (Internet Protocol) reputation is essentially a trust score assigned to the IP address from which your emails originate. It's like a credit score for email sending. Mailbox providers use this score to determine how likely your emails are to be legitimate and wanted, heavily influencing whether they land in the inbox, spam folder, or are rejected.
A good IP reputation affects email deliverability positively, ensuring high inbox placement rates. Conversely, a poor or low IP reputation can lead to emails being filtered, delayed, or outright blocked. Factors impacting IP reputation include sending volume consistency, spam complaint rates, bounce rates, and whether the IP has been used for malicious activities in the past. If you use a shared IP, the sending practices of others on that IP can also impact your reputation.
While domain reputation has gained more prominence, IP reputation remains a critical factor. Many ISPs and anti-spam organizations maintain blacklists (or blocklists) of IP addresses known for sending spam or suspicious mail. If your IP address ends up on one of these blocklists, your emails will likely be rejected by a significant number of recipients. Monitoring your Google Postmaster Tools metrics is essential.
What happens if your IP is blocklisted?
If your IP address appears on an email blocklist (or blacklist), it means your emails are likely to be rejected or sent to spam by mail servers that consult that list. This can severely impact your deliverability, leading to missed opportunities and damaged sender trust. Recovery often involves identifying the root cause, stopping the offending sending behavior, and requesting delisting from the relevant blocklist operator.
The interplay of factors and email rejections
While distinct, DMARC, spam complaints, and IP reputation collectively form the backbone of your email deliverability. A high IP and domain reputation might seem like a golden ticket, but if you have high spam complaints, even with passing DMARC, your emails will still struggle to reach the inbox.
DMARC helps protect your domain and ensures authenticated emails. However, as noted earlier, DMARC rejections are typically due to authentication failures, not spam classification. If you're seeing rejections tied to a DMARC reject policy, it points to an authentication issue, perhaps a legitimate sender not being properly authorized or a misconfiguration. This is different from emails being filtered to spam due to poor content or list hygiene, which is signaled by Google Postmaster Tools showing high spam complaint rates.
If you are experiencing a situation where your domain and IP reputation appear high, but you're still getting high spam complaints and delivery errors (especially DMARC-related ones), it often means there's a disconnect. You might have excellent sending infrastructure, but your email content or list quality is triggering spam filters. Alternatively, if email deliverability issues are specifically DMARC-related, it's crucial to examine your email headers to understand which domain is failing authentication and why, especially if you're using subdomains or sending on behalf of multiple entities. The bounce logs usually provide clues, indicating if the rejection is due to DMARC policy or a spam filter.
Views from the trenches
Best practices
Maintain meticulous list hygiene to minimize spam complaints and invalid addresses.
Implement DMARC with a `p=none` policy, then gradually move to `quarantine` or `reject` as you gain confidence.
Monitor your sender reputation using tools like Google Postmaster Tools.
Ensure all legitimate sending sources are properly authenticated with SPF and DKIM.
Segment your audience and tailor content to improve engagement and reduce spam reports.
Common pitfalls
Ignoring DMARC reports, missing critical authentication failures or unauthorized sending.
Sending to unengaged or old lists, leading to high bounce rates and spam complaints.
Failing to implement DMARC for main domains, leaving them vulnerable to spoofing.
Assuming high IP/domain reputation alone guarantees inbox delivery without addressing content quality.
Not having a clear unsubscribe process, forcing users to mark as spam.
Expert tips
Use subdomains for different sending types (e.g., transactional, marketing) to isolate reputation.
Regularly review your email headers for authentication alignment and potential issues.
Engage with recipients to build positive sending signals and reduce complaint rates.
Understand that DMARC rejections and spam folder placement are distinct issues.
Collaborate with IT to ensure DNS records are correctly configured and monitored.
Expert view
Expert from Email Geeks says the RUA tag is crucial for monitoring email activity on a domain, but it does not directly affect email deliverability.
2021-09-20 - Email Geeks
Expert view
Expert from Email Geeks says rejections due to DMARC policies are distinct from rejections or junking caused by high spam complaints; they are not directly linked.
2021-09-20 - Email Geeks
Achieving consistent inbox placement
Achieving consistent inbox placement and avoiding email rejections requires a holistic approach. It’s not enough to implement DMARC, or just keep spam complaints low, or only maintain a good IP reputation. All these factors work in tandem, and neglecting one can undermine the others. A robust DMARC implementation ensures your emails are authenticated and protects your brand from spoofing, while proactive spam complaint management protects your reputation from negative user feedback.
Regularly monitoring your DMARC reports, maintaining clean email lists, crafting engaging content, and keeping a close eye on your IP and domain reputation metrics are continuous tasks that pay dividends in deliverability. By understanding and managing these crucial elements, you can significantly improve your chances of reaching the inbox and maximizing your email program's effectiveness.
Gmail and 
Yahoo, are very sensitive to user feedback. If recipients consistently mark your emails as spam, your overall domain reputation will plummet. This then leads to emails being routed directly to the spam folder, or in severe cases, outright blocking (being added to a blocklist).
Gmail rarely reject emails for spam reasons alone, preferring to filter them to junk.
