Summary
When B2B clients report not receiving emails without bounce errors, it indicates a complex deliverability issue with numerous potential causes. These issues can stem from sender-side problems like poor sender reputation (due to low engagement, inconsistent sending volume, or poor list hygiene), authentication failures (incorrect SPF, DKIM, or DMARC records), or technical issues with the email content itself. Recipient-side factors also play a significant role, including the use of security solutions like Proofpoint or Barracuda, email client firewalls, greylisting or tarpitting mechanisms, and network configuration settings. It's also crucial to consider that ESPs may silently block emails due to historical complaints and that soft bounces may be occurring without explicit notification. Effective troubleshooting requires a comprehensive approach including analyzing SMTP error codes, examining sending logs, improving list hygiene, authenticating the sending domain, and if necessary, contacting the recipient's IT team.
Key findings
- Sender Reputation is Crucial: Low engagement rates (opens and clicks), spam complaints, inconsistent sending volume, and poor list hygiene all negatively impact sender reputation, leading to filtering or blocking.
- Authentication is Key: Incorrect or missing SPF, DKIM, and DMARC records can cause deliverability problems, hindering the ability to verify the legitimacy of emails.
- Recipient-Side Filtering is a Major Factor: Security solutions (Proofpoint, Barracuda), email client firewalls, greylisting, and tarpitting on the recipient's server can block or delay email delivery.
- Email Content Matters: Poorly coded emails with excessive HTML, broken links, or missing alt text can trigger spam filters.
- List Hygiene is Essential: Sending to old, unengaged contacts can increase bounce rates and spam complaints, damaging sender reputation.
- ESPs Can Block Silently: The sending ESP may silently drop emails due to historical complaints or global 'never send to' lists.
- Soft Bounces Provide Clues: The existence of soft bounces are not known and can assist with finding the issues.
Key considerations
- Check Sending Logs: Thoroughly examine email sending logs for acceptance, rejection, or delay messages, along with specific SMTP error codes.
- Verify Email Authentication: Ensure proper implementation and validation of SPF, DKIM, and DMARC records for email authentication.
- Improve List Hygiene: Regularly clean email lists by removing inactive subscribers and segmenting based on engagement.
- Send Personalized & Relevant Content: Personalize emails and tailor content to individual recipients to increase engagement and avoid spam triggers.
- Contact Recipient IT: If possible, establish communication with the recipient's IT team to whitelist the sender and troubleshoot potential filtering issues on their side.
- Review Email Code: Ensure the email code is clean, avoids excessive HTML, and includes alt text for all images.
- Monitor Sender Reputation: Use tools like Sender Score to proactively monitor sender reputation and identify/address potential issues.
- Monitor Soft Bounce Issues: Monitor SMTP responses and soft bounces to try and address underlying deliverability problems.
What email marketers say
11 marketer opinions
Emails not being received by B2B clients despite the absence of bounce errors is a complex issue with multiple potential causes. Several factors on both the sender's and receiver's ends can be responsible. These include issues with sender reputation (damaged by low engagement, spam complaints, inconsistent sending volume or poor list hygiene), authentication problems (incorrect SPF, DKIM, or DMARC records), technical issues (greylisting, tarpitting, or filtering on the recipient's server; problems with email code such as excessive HTML or broken links; or the ESP silently blocking delivery). Checking logs, verifying sender reputation, improving email content and authentication, cleaning email lists, and contacting the recipient's IT are crucial steps to resolving the issue.
Key opinions
- Sender Reputation: Low engagement, spam complaints, and inconsistent sending volume can harm sender reputation, leading to emails being filtered as spam.
- Authentication Issues: Incorrect or missing SPF, DKIM, and DMARC records can cause deliverability problems.
- Recipient-Side Filtering: Greylisting, tarpitting, and firewalls on the recipient's server can block or delay email delivery.
- Email Content Problems: Excessive HTML, broken links, and images without alt text in email code can trigger spam filters.
- List Hygiene: Sending to old, unengaged contacts can increase bounce rates and spam complaints.
- ESP Blocking: The ESP may silently drop emails due to historical complaints or global 'never send to' lists.
Key considerations
- Check Logs: Examine email sending logs to identify if messages are being accepted, rejected, or delayed.
- Verify Authentication: Ensure proper implementation of SPF, DKIM, and DMARC records to authenticate the sending domain.
- Improve Engagement: Segment email lists, clean inactive subscribers, and send relevant, personalized content to improve engagement rates.
- Contact Recipient's IT: If possible, contact the recipient's IT team to whitelist the sender and investigate potential filtering issues on their end.
- Review Email Code: Ensure the email code is clean, avoids excessive HTML, and includes alt text for images.
- Monitor Sender Reputation: Regularly monitor sender reputation using tools like Sender Score to identify and address potential issues.
Marketer view
Email marketer from Mailjet suggests that if emails aren't bouncing but also aren't being received, a potential cause is greylisting on the recipient's server. Greylisting temporarily rejects emails from unknown senders to combat spam, and legitimate servers should retry sending the email.
12 Jan 2023 - Mailjet
Marketer view
Marketer from Email Geeks suggests that if the recipient uses a hosted MX offering, messages might be silently dropped before reaching on-site IT controls. Also, the ESP might be silently dropping emails due to historical complaints. They advise checking if messages are being accepted (SMTP 250ed) and examining logs.
11 Jul 2021 - Email Geeks
What the experts say
3 expert opinions
Emails not being received by B2B clients despite the absence of bounce errors can be attributed to a few key areas. Firstly, the client may have security layers like Proofpoint or Barracuda that intercept emails before they reach the intended recipient or their IT team. Secondly, poor engagement, even without bounces, can severely damage sender reputation, leading to filtering or blocking by mailbox providers. Finally, email client firewalls may be filtering emails, so it's crucial to ensure sending IPs are not blacklisted.
Key opinions
- Security Layer Interception: Security solutions like Proofpoint or Barracuda can intercept emails before they reach the recipient or their IT department.
- Poor Engagement Impact: Low open and click rates negatively impact sender reputation, resulting in filtering or blocking.
- Email Client Firewalls: Email client firewalls can filter emails, making it essential to verify sending IPs are not blacklisted.
Key considerations
- Investigate Security Layers: Explore if the client is using security solutions that might be intercepting emails.
- Improve Engagement Metrics: Focus on improving email engagement metrics to maintain a positive sender reputation.
- Check Blacklists: Regularly check sending IPs against blacklists to ensure they are not being blocked.
Expert view
Expert from Spam Resource explains that there could be email client firewalls that are being used which are filtering the emails. Ensure that your sending IPs are not on any blacklists.
11 Mar 2025 - Spam Resource
Expert view
Expert from Email Geeks suggests the client might have a layer like Proofpoint or Barracuda intercepting emails before they reach the IT team.
28 Dec 2021 - Email Geeks
What the documentation says
5 technical articles
When emails are not received by B2B clients without generating bounce errors, the issue often stems from authentication problems, recipient-side network configurations, or a failure to properly interpret SMTP feedback. Ensuring correct SPF, DKIM, and DMARC implementation is critical for authentication. Recipient firewalls and network settings can also block emails, and the user should ensure IP addresses are allowed and DNS records are accurate. Finally, soft bounces may be occurring without the user's knowledge.
Key findings
- Authentication: Proper SPF, DKIM, and DMARC implementation are crucial for preventing emails from being marked as spam.
- Network Configuration: Recipient-side firewalls and network configurations can block incoming emails.
- SMTP Error Codes: Understanding SMTP error codes is important for troubleshooting delivery issues.
- DMARC Records: Incorrect or missing DMARC records can cause email deliverability problems and the DMARC policy is correct.
- Soft Bounces: Soft bounces may be occurring without the user being aware, indicating underlying deliverability issues.
Key considerations
- Verify Authentication: Double-check SPF, DKIM, and DMARC records to ensure they are correctly configured.
- Check Network Settings: Collaborate with the recipient's IT team to review firewall rules and network configurations.
- Monitor SMTP Responses: Implement monitoring to capture and analyze SMTP error codes for insights into delivery problems.
- Analyse soft bounces: Implement monitoring to capture and analyse soft bounces to help identify issues.
Technical article
Documentation from Microsoft Learn explains that network configurations and firewall settings on the recipient's end can block incoming emails. They recommend checking firewall rules, allowing necessary IP addresses, and ensuring proper DNS records.
28 Mar 2024 - Microsoft Learn
Technical article
Documentation from DMARC.org details that incorrect or missing DMARC records can cause email deliverability problems. Implementing DMARC helps receiving mail servers verify the legitimacy of emails and reduces the risk of spoofing. A DMARC policy of 'none' may cause issues.
11 Feb 2022 - DMARC.org
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