Summary
Even after resolving IP address issues, persistent email deliverability problems stem from a confluence of factors. These include sender reputation, heavily influenced by user engagement and list hygiene; email content, which can trigger spam filters based on wording and formatting; the implementation and correctness of email authentication protocols (SPF, DKIM, DMARC); sending practices, particularly suspicious activities like using G-Suite for outreach; and external factors such as being listed on blacklists or sharing an IP address with problematic senders. Experts emphasize a comprehensive, holistic approach, stressing continuous monitoring of engagement metrics, testing across different email clients, actively managing sender reputation, and utilizing feedback loops to identify and address issues.
Key findings
- Sender Reputation Matters: Past negative engagement and poor list hygiene continue to impact deliverability even with a clean IP.
- Content is King (and Can Be Your Downfall): Specific words, phrases, and formatting choices can trigger spam filters regardless of IP health.
- Authentication is Crucial: Proper SPF, DKIM, and DMARC implementation is essential for verifying sender identity and preventing spoofing.
- Holistic Approach is Needed: Technical setup alone isn't enough; content, engagement, and list hygiene are equally important.
- Blacklists Can Linger: IP or domain may still be blacklisted even after the original issue is fixed.
- Shared IPs Can Be Problematic: Actions of other senders on a shared IP can negatively affect your deliverability.
- Algorithms are Complex: Gmail's and Outlooks complex algorithms consider user reports, recipient interactions and a variety of other factors.
- Best Guess SPF Can Help: Gmail can help you with its best guess SPF mitigation.
Key considerations
- Actively Manage Sender Reputation: Focus on building and maintaining a positive sender reputation through consistent positive engagement.
- Optimize Email Content: Carefully review and optimize email content to avoid spam triggers.
- Implement Robust Email Authentication: Ensure proper setup and validation of SPF, DKIM, and DMARC records.
- Practice Diligent List Hygiene: Regularly clean email lists to remove inactive or invalid addresses.
- Warm Up New IPs Gradually: If using a new IP address, gradually increase sending volume to establish a positive sending reputation.
- Monitor Engagement Metrics Continuously: Track open rates, click-through rates, bounce rates, and spam complaints to identify and address deliverability issues.
- Test Emails Across Platforms: Test emails on different email clients and devices to identify rendering and spam filter issues.
- Utilize Feedback Loops: Implement feedback loops to receive notifications about spam complaints and address the underlying causes.
- Investigate Sending Practices: Review your current sending practices for suspicious activities that may harm sender reputation.
What email marketers say
10 marketer opinions
Even after fixing IP address issues, email deliverability can still suffer due to a multitude of factors. These include sender reputation (impacted by past engagement and list hygiene), content that triggers spam filters, lack of proper email authentication (SPF, DMARC), shared IP address issues, blacklist status, and the absence of an IP warming strategy. Monitoring engagement metrics, testing emails, and utilizing feedback loops are also crucial for identifying and addressing deliverability problems.
Key opinions
- Sender Reputation: A damaged sender reputation, even after fixing IP issues, takes time to rebuild through consistent positive engagement (opens, clicks).
- Content Triggers: Certain words, phrases, and formatting can trigger spam filters, regardless of IP reputation.
- List Hygiene: Sending to inactive or invalid addresses negatively impacts sender reputation and deliverability.
- Email Authentication: Lack of proper SPF, DKIM, and DMARC configuration can lead to emails being marked as spam.
- IP Warming: New or damaged IP addresses require a gradual warming process to establish a positive sending reputation.
- Blacklist Status: IP address or domain may still be listed on blacklists even after the original issue is resolved.
- Shared IP Issues: On a shared IP, the actions of other senders can negatively impact your deliverability.
Key considerations
- Monitor Engagement: Track open rates, click-through rates, and spam complaints to identify deliverability issues.
- Email Testing: Test emails across different clients and devices to identify rendering issues and spam triggers.
- Feedback Loops (FBLs): Implement FBLs to receive notifications of spam complaints and address underlying problems.
- Authenticate Email: Ensure SPF, DKIM and DMARC authentication settings are configured correctly to help prove you are who you say you are.
Marketer view
Email marketer from Sendgrid shares that utilizing feedback loops (FBLs) allows you to receive notifications when recipients mark your emails as spam. This enables you to identify and address issues that are contributing to spam complaints.
1 Oct 2022 - Sendgrid
Marketer view
Email marketer from Reddit explains that certain words, phrases, and formatting choices can trigger spam filters. Reviewing email content for potential spam triggers is crucial, even if the IP issue is resolved.
4 Apr 2023 - Reddit
What the experts say
5 expert opinions
Even after fixing IP address issues, email deliverability can continue to be affected by various factors, including suspicious sending activities (like using G-Suite for outreach), content choices, overall sender reputation, list hygiene, recipient engagement, and proper technical setup (SPF, DKIM, DMARC). Experts emphasize a holistic approach to deliverability, highlighting the importance of consistent monitoring of engagement metrics and addressing potential issues with content, sending practices, and IP/domain reputation.
Key opinions
- Suspicious Sending Activities: Using G-Suite or similar platforms for mass outreach can negatively impact sender reputation.
- Holistic Approach: Even with correct technical setup (SPF, DKIM, DMARC), deliverability can fail due to content, list hygiene, and recipient engagement.
- Content and Reputation: Content choices and overall sender reputation are key determinants of deliverability after fixing IP issues.
- Transactional Email Issues: Transactional emails may land in spam due to lack of dedicated IPs, high complaint rates, or problematic content.
- SPF & DKIM Impact: Missing or broken SPF/DKIM can impact deliverability - however Gmail's best guess SPF can help.
Key considerations
- Investigate Sending Activities: Review and adjust sending practices to avoid activities that may be flagged as suspicious.
- Monitor Engagement: Consistently track engagement metrics (opens, clicks, complaints) to identify and address deliverability issues.
- Content Review: Analyze email content for potential spam triggers and make necessary adjustments.
- Dedicated IPs: Consider using dedicated IPs, especially for transactional emails, to improve reputation and control.
- Implement Technical Setup: Ensure that you implement SPF, DKIM and DMARC to help improve deliverability.
Expert view
Expert from Word to the Wise, Dennis Dayman, explains that transactional emails may land in spam due to a lack of dedicated IPs, high complaint rates, or content issues. The IP and domain reputation is crucial for all types of email.
11 Jan 2023 - Word to the Wise
Expert view
Expert and Marketer from Email Geeks discuss the impact of SPF and DKIM on email deliverability, with Ken suggesting that missing or broken SPF, without DKIM signing, could cause issues with Gmail, while Laura notes Gmail's 'best guess SPF' which mitigates broken SPF records. Ken then agreed that it could be multiple factors, and authentication tips it over the edge.
11 Apr 2022 - Email Geeks
What the documentation says
5 technical articles
Even after fixing IP address issues, email deliverability can still be hindered by various factors recognized by major email providers like Gmail and Outlook. These include sender reputation (influenced by user reports and past engagement), email content, and, critically, the proper implementation of email authentication standards (SPF, DKIM, DMARC). Documentation emphasizes that misconfigured or missing authentication records can lead to emails being classified as spam, regardless of IP reputation.
Key findings
- Gmail's Algorithm: Gmail's spam filtering considers user reports, sender reputation, and content, meaning a clean IP alone doesn't guarantee inbox placement.
- Outlook's Evaluation: Outlook evaluates sender authentication (SPF, DKIM, DMARC), content, and recipient interactions, highlighting the importance of a comprehensive approach.
- SPF Configuration: Correct SPF configuration is crucial for verifying the sender's identity and preventing deliverability issues.
- DMARC Implementation: Proper DMARC implementation protects against email spoofing and improves deliverability by providing instructions to receiving servers on handling failed SPF/DKIM checks.
- DKIM Signing: Proper DKIM signing is critical in verifying the authenticity of email and preventing emails failing checks being marked as spam.
Key considerations
- Sender Reputation Management: Actively manage sender reputation by engaging recipients positively and avoiding spam triggers.
- Content Optimization: Review email content for potential spam triggers and optimize for readability and engagement.
- Authentication Verification: Ensure correct configuration of SPF, DKIM, and DMARC records to authenticate emails properly.
- Continuous Monitoring: Regularly monitor deliverability metrics and make adjustments as needed to maintain optimal inbox placement.
Technical article
Documentation from Microsoft Support details that Outlook's spam filter evaluates various factors, including the sender's authentication (SPF, DKIM, DMARC), the content of the email, and the recipient's past interactions with the sender. Insufficient or incorrect authentication can lead to emails being marked as spam.
24 Apr 2025 - Microsoft Support
Technical article
Documentation from DKIM.org emphasises that DomainKeys Identified Mail (DKIM) provides a method for verifying the authenticity of email messages. Improper DKIM signing can cause emails to fail authentication checks and be marked as spam.
5 Jan 2022 - DKIM.org
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