Summary
Transactional emails are often filtered into the junk folder due to a combination of factors related to sender reputation, authentication, content, and user engagement. Poor sender reputation, influenced by IP and domain reputation and negative signals like complaints, blacklists, and spam traps, is a significant cause. Lack of proper email authentication (SPF, DKIM, DMARC) makes it difficult for email providers to verify the legitimacy of the emails. Content that resembles spam, along with issues like sending to unengaged or invalid email addresses, also contributes to deliverability problems. User perception of the emails as non-transactional or unwanted leads to negative engagement and further damages sender reputation. ISPs may even reject emails they believe users don't want, or misinterpret interest as spam. Following best practices, such as authentication, sending emails people want, and correct formatting, are all crucial for inbox placement. Each customer should use their own domain for authentication, and SCL is not a scoring system. Implementing DMARC helps to protect domains from spoofing and phishing.
Key findings
- Sender Reputation is Key: Poor sender reputation, affected by IP/domain reputation, spam complaints, blacklists, and spam traps, is a primary reason for emails going to spam.
- Authentication is Crucial: Lack of proper email authentication (SPF, DKIM, DMARC) makes it difficult to verify email legitimacy.
- Content Matters: Spam-like content increases the likelihood of emails being filtered as spam.
- User Engagement Affects Delivery: Negative user engagement, such as being marked as spam or ignored, hurts sender reputation.
- List Hygiene is Essential: Sending to unengaged or invalid email addresses damages sender reputation and deliverability.
- Customer Domains: Each customer should use their own domain for authentication and click links, rather than a subdomain of the service provider.
- Filtering is Complex: Email filtering is complex and influenced by many factors from reputation to blacklists.
Key considerations
- Improve Sender Reputation: Actively work to improve and maintain a positive sender reputation by addressing factors like spam complaints, blacklisting, and IP/domain reputation.
- Implement Authentication: Implement proper email authentication (SPF, DKIM, DMARC) to verify the legitimacy of emails.
- Clean Up Email Lists: Regularly clean email lists to remove unengaged or invalid email addresses.
- Optimize Email Content: Review and optimize email content to avoid triggers that may cause spam filters.
- Encourage User Engagement: Encourage positive user engagement with emails to improve sender reputation.
- Monitor and Address Problems: Actively monitor email delivery metrics and address any deliverability problems promptly.
- Authentication Best Practices: Follow all the rules: authenticate, send email people want, and format correctly.
- Filter Indicators: Address all factors affecting email filtering, including authentication, engagement, and complaints.
What email marketers say
12 marketer opinions
Transactional emails often land in the junk folder due to several interconnected factors. Poor sender reputation, influenced by IP and domain reputation, is a primary culprit. This can stem from issues like being blacklisted, high spam complaint rates, sending to unengaged or invalid email addresses, and using content that triggers spam filters. A lack of proper email authentication (SPF, DKIM, DMARC) also makes it harder for email providers to verify the legitimacy of your emails. User engagement plays a significant role, as negative engagement (ignoring emails) or users marking emails as spam damages your sender reputation. Maintaining clean email lists, using a dedicated IP address, and actively monitoring sender reputation are crucial for improving deliverability.
Key opinions
- Sender Reputation: Poor sender reputation, influenced by IP and domain reputation, is a primary cause of transactional emails going to spam.
- Email Authentication: Lack of proper authentication (SPF, DKIM, DMARC) makes it harder for email providers to verify email legitimacy.
- User Engagement: Negative user engagement (ignoring emails) or users marking emails as spam damages sender reputation.
- Content Triggers: Using content that triggers spam filters increases the likelihood of emails landing in the junk folder.
- List Hygiene: Sending to unengaged or invalid email addresses negatively impacts deliverability.
Key considerations
- Monitor Reputation: Actively monitor sender reputation metrics and take corrective action when necessary.
- Implement Authentication: Ensure proper email authentication (SPF, DKIM, DMARC) is in place.
- Clean Email Lists: Regularly clean email lists to remove unengaged and invalid email addresses.
- Content Optimization: Optimize email content to avoid triggers that may lead to spam filtering.
- Dedicated IP: Consider using a dedicated IP address to build and maintain a positive sender reputation.
- Encourage Engagement: Focus on increasing positive user engagement (opens, clicks) with your transactional emails.
Marketer view
Email marketer from Reddit explains that transactional emails often end up in the spam folder due to poor sender reputation, failure to properly authenticate emails (SPF, DKIM, DMARC), and content that triggers spam filters. They also noted that factors such as high spam complaint rates and sending to outdated or unengaged email lists can significantly impact deliverability and increase the likelihood of emails being categorized as spam.
5 Sep 2023 - Reddit
Marketer view
Email marketer from Stack Overflow explains that IP reputation is a crucial factor influencing transactional email delivery. They state that if your sending IP address is blacklisted or has a poor reputation, email service providers may filter your emails into the spam folder. They advise monitoring IP reputation and taking measures to improve it, such as authenticating emails and avoiding spam-like content.
13 Jun 2024 - Stack Overflow
What the experts say
5 expert opinions
Transactional emails can end up in the junk folder for a variety of reasons relating to sender identity, reputation, and content. Email providers use complex filtering systems that consider user complaints, blacklists, and engagement. Even legitimate emails can be rejected if the ISP questions the sender's legitimacy, if users don't want the email, or even if the ISP misinterprets user interest as spam. Domain and IP reputation are tied to identities, and shared identities will share reputation. Proper authentication, sending emails users want, and correct formatting are crucial for improving deliverability. SCL values record things, but they are not a score.
Key opinions
- Complex Filtering: Email providers use complex filtering systems considering complaints, blacklists, engagement, and other factors.
- Sender Identity: Domain and IP reputation are tied to identities, impacting deliverability.
- User Perception: ISPs may reject emails based on their perception of user desire or potential spam classification.
- Authentication & Formatting: Proper authentication and correct email formatting are crucial for delivery.
- SCL Purpose: SCL values record things, but they are not a score or used for the filtering systems.
- Domains: Each customer should use their own domain for authentication and click links, rather than a subdomain of the service provider.
Key considerations
- Authentication: Ensure proper email authentication (SPF, DKIM) using the customer's domain is implemented.
- Content & Value: Focus on sending emails that users want and find valuable to avoid rejection by ISPs.
- Reputation Management: Actively monitor and manage domain and IP reputation to avoid blacklisting or negative signals.
- Engagement: Encourage positive user engagement (opens, clicks) to improve sender reputation.
- Filter Signals: Address the many factors that contribute to email filtering, including complaints, blacklists, honeypots, spam traps, authentication and engagement.
Expert view
Expert from Email Geeks initially suggests content-based filtering might be the reason for emails going to spam, based on user reports. Expert from Email Geeks later stated that there are domains and IPs that are so toxic, it will cause delivery to fail, even with domains of high reputation. She clarified that identities (IPs and authenticated domains) are used as hooks for reputation, and shared identities will share reputation.
18 Apr 2023 - Email Geeks
Expert view
Expert from Email Geeks stated SCL values are not a score, it is something that just records things.
1 Mar 2022 - Email Geeks
What the documentation says
4 technical articles
Transactional emails are often marked as spam due to several technical and reputational factors. Google highlights issues like similarity to spam, suspicious IP addresses, and incorrect authentication. The RFC-Editor emphasizes implementing proper authentication mechanisms (SPF, DKIM), maintaining good sender reputation, and monitoring spam complaints. Microsoft's SCL rating indicates spam likelihood, influenced by spam filtering settings. DMARC is essential for protecting domains from spoofing and phishing, working with SPF and DKIM to verify authenticity and improve deliverability.
Key findings
- Authentication: Lack of proper authentication (SPF, DKIM, DMARC) contributes to emails being marked as spam.
- Sender Reputation: Poor sender reputation, influenced by factors such as spam complaints and blacklisting, leads to deliverability issues.
- Content Similarity: Emails resembling spam are more likely to be filtered as spam.
- Suspicious IPs: Emails originating from suspicious IP addresses are more likely to be marked as spam.
- Spoofing Protection: DMARC is essential for preventing email spoofing and phishing attacks.
Key considerations
- Implement Authentication: Ensure proper email authentication mechanisms (SPF, DKIM, DMARC) are in place.
- Monitor Reputation: Actively monitor sender reputation metrics and address any issues proactively.
- Optimize Content: Review email content to avoid characteristics that resemble spam.
- IP Reputation: Ensure your sending IP address has a good reputation and isn't blacklisted.
- Configure SCL: Configure spam filtering settings to manage and control SCL thresholds.
Technical article
Documentation from Google Workspace Admin Help explains that Google marks emails as spam for a number of reasons including the email being similar to other spam messages, the email coming from a suspicious IP address, the email not being authenticated correctly, and the email having a high complaint rate.
16 Apr 2025 - Google Workspace Admin Help
Technical article
Documentation from Microsoft Learn explains that the SCL Spam Confidence Level, is a rating that indicates the likelihood of an email being spam. A higher SCL indicates a greater probability of the email being spam, leading to the email being filtered into the junk folder. They highlight the importance of configuring spam filtering settings to manage and control SCL thresholds effectively, which helps ensure that legitimate transactional emails are not mistakenly marked as spam.
6 Jun 2024 - Microsoft Learn
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