Summary
Even when transactional emails pass SPF, DKIM, and DMARC, they can still land in spam due to a variety of factors beyond authentication. These include content and audience issues, infrastructure problems like incorrect rDNS records, and poor sender reputation built from low engagement, spam complaints, and high bounce rates. Suspicious email content, blacklisted IP addresses, and using 'no-reply' addresses also contribute. New IP addresses require gradual warming up, and maintaining a clean email list is crucial. Sudden sending volume spikes or using shared IP addresses can trigger spam filters. DMARC policy enforcement, appropriate DKIM key length and feedback loops play a role as well. Mailbox providers like Gmail and Microsoft consider various factors beyond authentication: user reports, content, and sending patterns. Finally, dev testing practices can significantly impact the reputation of the email program. In essence, authentication is just one piece; sender reputation, content quality, infrastructure and sending practices all play significant roles.
Key findings
- Sender Reputation: A poor sender reputation due to low engagement, spam complaints, or high bounce rates can cause emails to land in spam.
- Content and Audience: Issues likely stem from content problems or incorrect audience targeting, especially with testing content. Spam filters analyze email content for suspicious keywords, excessive capitalization, and poor HTML coding.
- Infrastructure: Incorrect rDNS records and other infrastructure issues can impact deliverability, even with proper authentication.
- IP Reputation: If the sending IP address is on a blocklist, emails will likely land in spam, regardless of authentication. Also sharing an IP can impact deliverability
- Engagement Rates: Low engagement rates (opens, clicks) can negatively impact deliverability.
- No-Reply Addresses: Using a 'no-reply' email address can negatively impact deliverability due to discouraged engagement.
- IP Warm-up: New IP addresses require gradual warming up to avoid triggering spam filters.
- List Hygiene: Maintaining a clean email list by removing inactive subscribers and invalid email addresses is crucial.
- Sending Volume: Sudden spikes in sending volume can trigger spam filters.
- DMARC Policy: A DMARC policy of 'none' only monitors and doesn't actively filter spam.
- DKIM Key Length: Using an appropriate DKIM key length (at least 1024-bit) is crucial for security and deliverability.
- Feedback Loops: Feedback loops (FBLs) allow senders to identify and remove subscribers marking emails as spam.
- Dev Testing: Automated dev testing practices generating uninterested emails can negatively impact engagement metrics and sender reputation.
- Gmail Filters: Gmail's spam filters consider factors beyond authentication: user reports, content, and sending patterns.
- Microsoft SmartScreen: Microsoft's SmartScreen filter uses machine learning to identify spam, recommending best practices for bulk email.
Key considerations
- Monitor Reputation: Regularly monitor your sender reputation and address any issues promptly.
- Optimize Content: Ensure email content is relevant, engaging, and avoids spam triggers.
- Verify Infrastructure: Verify your rDNS records and ensure your infrastructure is properly set up. Check IP for AWS space issues
- IP Monitoring: Check your IP address against blocklists and take steps to remove it if necessary.
- Boost Engagement: Implement strategies to improve email engagement, such as personalization and relevant content.
- Avoid No-Reply: Consider using a real reply-to address to encourage engagement.
- Warm-up New IPs: If using a new IP address, gradually warm it up to establish a good sending reputation.
- Maintain List Hygiene: Regularly clean your email list to remove inactive or invalid addresses.
- Control Sending Volume: Avoid sudden spikes in sending volume and maintain a consistent sending pattern.
- Use Strong DKIM Keys: Ensure you are using a sufficiently strong DKIM key length (at least 1024-bit).
- Enforce DMARC: Implement a stricter DMARC policy (quarantine or reject) after careful monitoring.
- Implement FBLs: Set up feedback loops with mailbox providers to monitor spam complaints and remove problematic subscribers.
- Dedicated IP: Consider using a dedicated IP address for greater control over your sending reputation.
- Separate Dev Testing: Isolate dev testing to a separate subdomain to prevent damaging your main domain's reputation.
- Follow Microsoft Guidelines: Adhere to Microsoft's best practices for bulk email, including list hygiene and unsubscribe options.
- Content Check: Use aboutmy.email to check content issues.
What email marketers say
9 marketer opinions
Even when transactional emails pass SPF, DKIM, and DMARC authentication, they can still land in spam due to various factors. These include a poor sender reputation built from low engagement, spam complaints, and high bounce rates. Suspicious email content, blacklisted IP addresses, and using 'no-reply' addresses also contribute. New IP addresses require gradual warming up, and maintaining a clean email list is crucial. Sudden sending volume spikes or using shared IP addresses can trigger spam filters. Essentially, authentication is just one piece of the deliverability puzzle; sender reputation, content quality, and sending practices all play significant roles.
Key opinions
- Sender Reputation: A poor sender reputation due to low engagement, spam complaints, or high bounce rates can cause emails to land in spam.
- Email Content: Spam filters analyze email content for suspicious keywords, excessive capitalization, and poor HTML coding.
- IP Reputation: If the sending IP address is on a blocklist, emails will likely land in spam, regardless of authentication.
- Engagement Rates: Low engagement rates (opens, clicks) can negatively impact deliverability.
- No-Reply Addresses: Using a 'no-reply' email address can negatively impact deliverability due to discouraged engagement.
- IP Warm-up: New IP addresses require gradual warming up to avoid triggering spam filters.
- List Hygiene: Maintaining a clean email list by removing inactive subscribers and invalid email addresses is crucial.
- Sending Volume: Sudden spikes in sending volume can trigger spam filters.
- Shared IPs: Using a shared IP address can impact deliverability due to the reputation of other users on the same IP.
Key considerations
- Monitor Reputation: Regularly monitor your sender reputation and address any issues promptly.
- Optimize Content: Ensure email content is relevant, engaging, and avoids spam triggers.
- IP Monitoring: Check your IP address against blocklists and take steps to remove it if necessary.
- Boost Engagement: Implement strategies to improve email engagement, such as personalization and relevant content.
- Avoid No-Reply: Consider using a real reply-to address to encourage engagement.
- Warm-up New IPs: If using a new IP address, gradually warm it up to establish a good sending reputation.
- Maintain List Hygiene: Regularly clean your email list to remove inactive or invalid addresses.
- Control Sending Volume: Avoid sudden spikes in sending volume and maintain a consistent sending pattern.
- Dedicated IP: Consider using a dedicated IP address for greater control over your sending reputation.
Marketer view
Email marketer from Litmus shares that low engagement rates (opens, clicks) can negatively impact deliverability. If subscribers are not interacting with transactional emails, mailbox providers may start filtering them as spam.
6 Sep 2022 - Litmus
Marketer view
Email marketer from Neil Patel explains that even with proper authentication, a poor sender reputation can cause emails to land in spam. Reputation is built over time based on subscriber engagement, spam complaints, and bounce rates.
8 Oct 2021 - Neil Patel
What the experts say
6 expert opinions
Even when transactional emails pass SPF, DKIM, and DMARC, deliverability issues can arise. The problem often stems from content issues, incorrect audience targeting, or infrastructure problems like improper rDNS setup. Dev testing practices that generate high volumes of uninterested emails can also negatively impact engagement, leading to spam placement. Furthermore, sudden increases in sending volume can trigger spam filters. Maintaining good engagement and proper infrastructure is key, regardless of authentication.
Key opinions
- Content and Audience: Issues likely stem from content problems or incorrect audience targeting, especially with testing content.
- Infrastructure: Incorrect rDNS records and other infrastructure issues can impact deliverability, even with proper authentication.
- Dev Testing: Automated dev testing practices generating uninterested emails can negatively impact engagement metrics.
- Engagement: Low engagement rates (opens, clicks, high deletion rates) signal to mailbox providers that recipients don't want the emails.
- Sending Volume: Sudden increases in sending volume can trigger spam filters.
Key considerations
- Review Content: Carefully review email content to ensure it is relevant and avoids spam triggers.
- Target Audience: Ensure you are targeting the correct audience with relevant emails.
- Verify Infrastructure: Verify your rDNS records and ensure your infrastructure is properly set up.
- Separate Dev Testing: Isolate dev testing to a separate subdomain to prevent damaging your main domain's reputation.
- Monitor Engagement: Monitor engagement metrics and adjust sending practices accordingly.
- Ramp Up Sending: Avoid sudden increases in sending volume; gradually ramp up sending as needed.
Expert view
Expert from Spam Resource answers that if you've recently increased your sending volume, it's possible that filters are reacting to this change, even if you have proper authentication in place. Sudden increases in volume can be seen as a sign of spam.
23 Nov 2022 - Spam Resource
Expert view
Expert from Email Geeks explains if emails are landing in spam despite passing authentication, the issue is likely with content or audience. If it is testing content it is likely a content issue. She also suggests ensuring the rDNS is correctly setup and not a random IP in AWS space and suggests using aboutmy.email to check.
29 Sep 2022 - Email Geeks
What the documentation says
5 technical articles
Even when transactional emails pass SPF, DKIM, and DMARC, they can still land in spam. This is because mailbox providers like Gmail and Microsoft consider factors beyond authentication, such as user reports, content, and sending patterns. A DMARC policy of 'none' only monitors authentication and doesn't enforce spam filtering. Using an appropriate DKIM key length is also crucial for security. Setting up feedback loops (FBLs) is valuable for identifying and removing subscribers who mark emails as spam, improving deliverability.
Key findings
- Gmail Filters: Gmail's spam filters consider factors beyond authentication: user reports, content, and sending patterns.
- DMARC Policy: A DMARC policy of 'none' only monitors and doesn't actively filter spam.
- Microsoft SmartScreen: Microsoft's SmartScreen filter uses machine learning to identify spam, recommending best practices for bulk email.
- DKIM Key Length: Using an appropriate DKIM key length (at least 1024-bit) is crucial for security and deliverability.
- Feedback Loops: Feedback loops (FBLs) allow senders to identify and remove subscribers marking emails as spam.
Key considerations
- Optimize for Gmail: Focus on content quality, user engagement, and consistent sending patterns to improve Gmail deliverability.
- Enforce DMARC: Implement a stricter DMARC policy (quarantine or reject) after careful monitoring.
- Follow Microsoft Guidelines: Adhere to Microsoft's best practices for bulk email, including list hygiene and unsubscribe options.
- Use Strong DKIM Keys: Ensure you are using a sufficiently strong DKIM key length (at least 1024-bit).
- Implement FBLs: Set up feedback loops with mailbox providers to monitor spam complaints and remove problematic subscribers.
Technical article
Documentation from RFC 7489 (DMARC standard) explains that a DMARC policy of 'none' only monitors authentication results and does not instruct receiving mail servers to reject or quarantine messages that fail authentication. A stricter policy of 'quarantine' or 'reject' can improve deliverability but requires careful monitoring.
8 Oct 2021 - RFC Editor
Technical article
Documentation from SparkPost shares the value of setting up feedback loops (FBLs) with mailbox providers to receive notifications when subscribers mark emails as spam. This allows senders to identify and remove problematic subscribers from their lists.
13 May 2023 - SparkPost
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