Summary
Even with SPF and DKIM authentication, low-volume emails often end up in spam due to factors affecting sender reputation and trust. These include low engagement, inconsistent sending patterns, problematic email content, poor list hygiene, and IP-related issues. Mailbox providers consider various signals, including sender reputation, user feedback, content characteristics, and the proper implementation of authentication protocols like DMARC. A new ESP or subdomain, strict DMARC policies, and missing reverse DNS records can also contribute to deliverability problems. Seed listing and IP warm-up are critical for establishing a positive sending reputation, especially for low-volume senders.
Key findings
- Sender Reputation is Key: Low sender reputation is a primary cause, driven by low engagement, complaints, inconsistent volume, and poor list hygiene.
- Authentication Alone Isn't Enough: SPF and DKIM are necessary but not sufficient. DMARC builds upon them, but even with all three, spam filters still consider content and engagement.
- Content Matters: Spam trigger words, poor HTML, and high image-to-text ratios flag emails, even with proper authentication.
- Low Volume Can Hurt: Very low volume and infrequent sending patterns can damage sender reputation, even from a legitimate sender.
- IP Reputation Influences: New or shared IP addresses may have poor reputations. Proper IP warm-up is crucial.
- Technical Issues Can Hinder: Missing or misconfigured reverse DNS records and incorrect IPv6 configurations can negatively impact deliverability.
Key considerations
- Monitor Engagement: Track open rates, click rates, and spam complaints to identify and address deliverability issues.
- Optimize Content: Avoid spam trigger words, use clean HTML, and balance images with text.
- Clean Your List: Regularly remove unengaged subscribers and invalid addresses.
- Warm Up New IPs: Gradually increase sending volume to establish a positive IP reputation.
- Establish a Consistent Schedule: Maintain a regular sending pattern for improved sender reputation.
- Implement DMARC Correctly: Ensure your DMARC policy doesn't inadvertently filter legitimate emails, and monitor its impact.
- Check Technical Settings: Verify correct reverse DNS records and proper IPv6 configuration.
- Consider Seed Listing: Monitor deliverability across different ISPs using a seed list.
- Use Feedback Loops: Enroll in feedback loops to receive spam complaints and remove those recipients.
What email marketers say
10 marketer opinions
Even with SPF and DKIM in place, low-volume emails can still land in spam due to various factors impacting sender reputation. These include low engagement, inconsistent sending patterns, spam complaints, poor list hygiene, using a new or shared IP without proper warm-up, problematic email content (spam trigger words, poor HTML, high image-to-text ratio), missing or misconfigured reverse DNS records, and misleading sender information. Addressing these issues and actively monitoring deliverability metrics are crucial for improving inbox placement.
Key opinions
- Sender Reputation: A low sender reputation is a primary driver for emails going to spam, even with SPF and DKIM. Factors influencing reputation include engagement, complaints, and sending history.
- Email Content: Spam trigger words, poor HTML, and high image-to-text ratios in email content can cause emails to be flagged as spam filters.
- IP Reputation: New or shared IP addresses often have poor reputations initially. Gradual IP warming is essential for establishing a good sending reputation.
- List Hygiene: Sending emails to old, unengaged, or improperly acquired lists leads to high bounce rates and spam complaints, negatively affecting deliverability.
- Inconsistent Sending: Sporadic or inconsistent sending patterns can negatively impact sender reputation, as mailbox providers prefer consistent sending schedules.
- Reverse DNS: A missing or misconfigured reverse DNS (rDNS) record can hinder deliverability, as it's used to verify the sending server's identity.
Key considerations
- Engagement Metrics: Actively monitor open rates, click-through rates, and spam complaints to identify and address deliverability issues promptly.
- Content Optimization: Avoid spam trigger words, use clean HTML coding, and maintain a balanced image-to-text ratio in your email content.
- IP Warm-up: If using a new IP address, gradually increase sending volume to establish a positive sending reputation.
- List Management: Regularly clean your email list by removing unengaged subscribers and invalid email addresses to reduce bounce rates and spam complaints.
- Sending Frequency: Establish a consistent sending schedule to build trust with mailbox providers.
- rDNS Configuration: Ensure a properly configured reverse DNS record is in place to verify your sending server's identity.
- Feedback Loops: Enroll in feedback loops with major ISPs to receive notifications about spam complaints and remove complainers from your list.
- Sender Information: Use consistent and recognizable 'From' names and email addresses to build trust with recipients.
Marketer view
Email marketer from Stack Overflow suggests that having a missing or misconfigured reverse DNS record could be contributing to emails landing in spam, despite having SPF and DKIM records configured. A correct rDNS record helps to verify the identity of the sending server.
5 Apr 2023 - Stack Overflow
Marketer view
Email marketer from HubSpot shares that inconsistent sending patterns (e.g., sporadic emails) can negatively impact sender reputation. Maintaining a consistent sending schedule helps mailbox providers trust your emails.
25 Jun 2023 - HubSpot
What the experts say
6 expert opinions
Low-volume emails can still land in spam despite SPF and DKIM due to several factors related to sender reputation and ISP trust. Infrequent sending and limited recipient pools contribute to this issue. Newly implemented ESPs and subdomains may initially face deliverability challenges that improve over time with recipient engagement. DMARC policies, if too strict, can also inadvertently filter legitimate emails. Establishing a positive sending reputation through seed listing, consistent sending patterns, and proper IP address warm-up is crucial for improving deliverability.
Key opinions
- Low Volume Impact: Very low sending volume and infrequent sending to limited inboxes can negatively impact deliverability even with authentication.
- New ESP/Subdomain: Bringing a new ESP online or using a new subdomain often results in initial deliverability challenges that improve as engagement increases.
- DMARC Policies: Strict DMARC policies ('quarantine' or 'reject') can cause legitimate emails to be filtered if authentication issues are present.
- Consistency Matters: Inconsistent sending patterns can harm sender reputation, as ISPs prefer regular email patterns.
- IP Setup: Properly warmed-up and reputable IP addresses are essential, especially for dedicated IPs.
Key considerations
- Seed Listing: Use seed listing to monitor deliverability across various ISPs and identify potential issues early on.
- Recipient Engagement: Encourage recipients to mark emails as 'not spam' to improve sender reputation over time.
- Sending Consistency: Maintain a consistent sending schedule to build trust with ISPs.
- IP Warm-up: If using a dedicated IP, warm it up gradually to establish a positive reputation.
- DMARC Policy Review: Carefully review DMARC policies to ensure they don't inadvertently filter legitimate emails.
Expert view
Expert from Word to the Wise explains that seed listing helps to establish a positive sending reputation, especially when starting with low volumes. It involves sending to a small, trusted group of recipients across various ISPs to monitor deliverability and identify potential issues before sending to a larger audience.
3 Apr 2023 - Word to the Wise
Expert view
Expert from Word to the Wise explains the importance of a proper IP address set up. Steve Jones explains that if you're using a dedicated IP address, make sure it's properly warmed up and has a good reputation before sending even low volume emails.
4 Aug 2023 - Word to the Wise
What the documentation says
5 technical articles
Even with SPF and DKIM, low-volume emails can still be filtered as spam due to various factors considered by email providers. Gmail, Outlook, and others evaluate sender reputation, email content, user feedback, and the proper implementation of authentication protocols. SPF's limitations in handling forwarded emails necessitate the use of DMARC for comprehensive authentication. Proper IPv6 configuration can also enhance deliverability. Overall, technical configurations, content and reputation interplay to determine email placement.
Key findings
- Holistic Filtering: Email providers like Gmail and Outlook use multifaceted spam filters, considering sender reputation, content, user feedback, and authentication.
- SPF Limitations: SPF alone is insufficient as it can fail with email forwarding, necessitating DMARC for comprehensive authentication.
- DMARC Policy Impact: DMARC policies define how mailbox providers should handle emails failing authentication, influencing deliverability based on the chosen policy.
- IPv6 Importance: Proper IPv6 configuration, including appropriate DNS records (AAAA records), can improve email deliverability.
Key considerations
- Reputation Management: Actively manage your sender reputation by monitoring metrics and addressing any negative feedback or complaints.
- Comprehensive Authentication: Implement DMARC in conjunction with SPF and DKIM for robust email authentication.
- Content Scrutiny: Ensure email content is not flagged as spam by avoiding spam trigger words and adhering to best practices.
- IPv6 Configuration: Configure your email server for IPv6, including setting up the necessary AAAA DNS records.
- SNDS Monitoring: Consider joining Microsoft's Smart Network Data Services (SNDS) program to monitor IP reputation and identify potential deliverability issues in Outlook.
Technical article
Documentation from Google Support explains that Gmail's spam filters consider many factors, including sender reputation, authentication, email content, and user feedback. Even with authentication, if the content is similar to spam or users frequently mark emails from the sender as spam, Gmail may still filter the emails.
21 May 2024 - Google Support
Technical article
Documentation from Microsoft Support explains that Outlook filters consider the sender's reputation, content, and user complaints. Joining the Smart Network Data Services (SNDS) program can help monitor your IP reputation and identify potential issues.
3 Jul 2024 - Microsoft Support
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