Summary
Despite passing DKIM, SPF, and DMARC authentication, emails can still land in spam due to a multitude of interconnected factors. These factors encompass sender reputation (influenced by spam complaints, sending volume, and IP history), engagement levels (open rates, interaction), content quality (spam trigger words, image-to-text ratio, URL shorteners), list hygiene (spam traps, unengaged addresses), infrastructure issues (shared IP reputation, Return-Path configuration), DMARC alignment failures, and blacklisting. Local filters may also contribute to the problem. Addressing deliverability requires a holistic approach encompassing reputation management, list hygiene, content optimization, technical configuration, and continuous monitoring.
Key findings
- Sender Reputation is Paramount: Low sender reputation, arising from spam complaints or poor engagement, overrides the benefits of authentication.
- Engagement Drives Deliverability: Low engagement rates and sending to inactive addresses significantly harm deliverability.
- Content is Scanned for Spam Triggers: Spam filters meticulously analyze email content, scrutinizing elements such as trigger words, image-to-text ratio, and URL shorteners.
- Blacklisting Remains a Threat: IP or domain blacklisting can nullify the advantages of proper authentication.
- DMARC Alignment is Crucial: Failure of the 'from' domain to align with DKIM/SPF domains undermines DMARC compliance.
- Infrastructure Must Be Sound: Issues with Return-Path configuration, shared IP addresses, and other infrastructure aspects affect deliverability.
- Local Filters Interfere: Local filters can impact inbox placement regardless of general sending reputation and best practice.
Key considerations
- Actively Monitor Sender Reputation: Employ tools like Google Postmaster Tools to closely track sender reputation and swiftly address any issues.
- Prioritize List Hygiene Practices: Regularly clean your email lists to eliminate unengaged subscribers and mitigate the risk of hitting spam traps.
- Optimize Email Content Diligently: Thoroughly review email content to remove spam trigger words, carefully balance images with text, and avoid the use of URL shorteners.
- Routinely Check Blacklists: Periodically assess your sending IP and domain against reputable blacklists.
- Consider a Dedicated IP Address: Evaluate the possibility of transitioning to a dedicated IP address to gain greater control over your sender reputation.
- Verify DMARC Alignment Methodically: Confirm that the 'from' domain is precisely aligned with both the DKIM and SPF domains.
- Validate Return-Path Configuration: Scrutinize your Return-Path domain setup to ensure correct configuration and alignment with your sending domain.
- Address Local Filters Proactively: Address internal filters that are impacting on sending.
What email marketers say
8 marketer opinions
Even with proper email authentication (DKIM, SPF, and DMARC) in place, emails can still land in the spam folder due to several factors. These include poor sender reputation, low engagement rates, the use of spam trigger words or spammy content, blacklisting of your IP or domain, infrastructure issues, and misalignment of your sending domain and tracking link domain. Maintaining a clean and engaged email list, monitoring sender reputation, and avoiding spam trigger words are crucial for improving email deliverability.
Key opinions
- Sender Reputation: Poor sender reputation, stemming from spam complaints or low engagement, can cause emails to be filtered as spam.
- Engagement Matters: Low engagement rates and sending to inactive addresses contribute to deliverability problems.
- Content Analysis: Spam filters analyze email content for spam trigger words and other suspicious elements.
- Blacklisting: Your sending IP or domain may be blacklisted, causing deliverability issues even with authentication.
- Domain Alignment: Inconsistencies between the sending domain and the domain used for tracking links can trigger spam filters.
Key considerations
- List Hygiene: Regularly clean your email list to remove inactive or invalid addresses and avoid spam traps.
- Monitor Reputation: Monitor your sender reputation using tools like Google Postmaster Tools and address any issues promptly.
- Content Optimization: Avoid using spam trigger words, excessive exclamation points, and other elements that might flag your email as spam.
- Check Blacklists: Periodically check your sending IP and domain against public blacklists (DNSBLs).
- Consider Dedicated IP: If using a shared IP address, consider switching to a dedicated IP to manage your own reputation.
- IP Warming: Warm up new IP addresses gradually before sending a large volume of emails to establish a positive reputation.
- Track records and correct setup: Ensure that you have the correct DNS records setup (SPF, DKIM, DMARC), and have checked they are valid using online tools.
Marketer view
Email marketer from Mailjet explains that even with proper authentication (DKIM, SPF, DMARC), emails can still land in spam due to factors like poor sender reputation, low engagement, spammy content, blacklisting, and infrastructure issues. They recommend monitoring sender reputation, cleaning email lists, improving engagement, and avoiding spam trigger words.
16 Sep 2024 - Mailjet
Marketer view
Email marketer from EmailMarketingForum.com suggests that you should check your sending IP against various DNS-based blackhole lists (DNSBLs). Even if you've set up DKIM, SPF, and DMARC correctly, your emails might still end up in the spam folder if your IP has been blacklisted.
20 Mar 2025 - EmailMarketingForum.com
What the experts say
5 expert opinions
Even with proper authentication (DKIM, SPF, DMARC), emails can still land in spam due to a variety of issues. These include: a poor sending reputation stemming from low engagement or high complaint rates; issues with email content, such as using URL shorteners or having a high image-to-text ratio; and poor list hygiene, which involves sending to unengaged addresses or spam traps. Internal or local filters may also incorrectly classify emails as spam, even if seed list tests show good inbox placement.
Key opinions
- Engagement & Reputation: Low engagement rates and a negative sender reputation are significant drivers of spam filtering, even with proper authentication.
- Content Matters: Email content, including the use of URL shorteners, image-heavy emails, and image-to-text ratio, plays a crucial role in deliverability.
- List Hygiene is Essential: Poor list hygiene, such as sending to unengaged addresses or spam traps, undermines deliverability.
- Local Filters: Local or internal filters can incorrectly classify emails as spam, independent of broader inbox placement.
Key considerations
- Monitor Engagement: Closely monitor open rates and engagement metrics to identify and address potential reputation issues.
- Optimize Content: Avoid using URL shorteners, balance images with text, and ensure content is not flagged as spammy.
- Clean Email Lists: Regularly clean your email lists to remove unengaged subscribers and avoid spam traps.
- Investigate Local Filters: If internal recipients are consistently receiving emails in spam, investigate local filter settings and configurations.
- Check MX Records: Ensure that mail is originating from MX records
Expert view
Expert from Email Geeks suggests that if open rates are high (40%+) then the seed list results may not be reflective of actual inbox placement. However, if open rates are lower, it may indicate an engagement/reputation issue.
29 Oct 2024 - Email Geeks
Expert view
Expert from Email Geeks suggests the issue might be local filters, especially if seed list tests show 100% inboxing and open rates are high. Filters might be affecting mail from the domain that doesn't originate from the MX records, so it's worth investigating.
8 Jan 2025 - Email Geeks
What the documentation says
6 technical articles
Even with DKIM, SPF, and DMARC in place, email deliverability can be hampered by a number of factors. These include low sender reputation (influenced by spam complaints, sending volume, and IP history), DMARC alignment failures (where the 'from' domain doesn't align with DKIM/SPF), being on blocklists, inconsistent sending volumes, high bounce and complaint rates, issues with the Return-Path domain, and problematic email content and structure (excessive images or large attachments).
Key findings
- Sender Reputation: Low sender reputation is a critical factor, even with proper authentication.
- DMARC Alignment: DMARC authentication can fail if the 'from' domain does not align with the DKIM or SPF domain.
- Blocklists & Sending Volume: Being on blocklists or sending inconsistent volumes can trigger spam filters.
- Bounce & Complaint Rates: High bounce and complaint rates negatively impact sender reputation and deliverability.
- Return-Path Configuration: An incorrectly configured Return-Path domain affects deliverability.
- Content Structure: Excessive images or large attachments can trigger spam filters.
Key considerations
- Monitor Sender Reputation: Use tools like Google Postmaster Tools to monitor your sender reputation.
- Ensure DMARC Alignment: Verify that the 'from' domain aligns with the DKIM and SPF domains.
- Check for Blocklisting: Regularly check if your sending IP is on any blocklists.
- Maintain Consistent Volume: Avoid sudden spikes in sending volume, and maintain a consistent sending cadence.
- Manage Bounce & Complaint Rates: Regularly clean your email lists to minimize bounce rates and address spam complaints promptly.
- Verify Return-Path Setup: Ensure your Return-Path domain is correctly configured and aligns with your sending domain.
- Optimize Content: Optimize email content by avoiding excessive images, large attachments, and spam trigger words.
Technical article
Documentation from AWS shares that you need to maintain low bounce rates by regularly cleaning your email lists. High bounce rates can signal that you're sending emails to outdated or invalid addresses, which can negatively affect your sending reputation and cause your emails to be marked as spam.
24 Mar 2024 - AWS
Technical article
Documentation from Microsoft shares that to avoid spam filters, ensure your sending IP is not on any blocklists, use a consistent sending volume, monitor bounce rates, and provide clear unsubscribe options. High complaint rates can negatively impact your sender reputation and lead to emails being filtered as spam.
28 Sep 2024 - Microsoft
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