Summary
When a customer reports not receiving marketing emails, even after their IT team confirms safelisting your domain, it can be a frustrating and perplexing situation. Your email service provider (ESP) might show the emails as sent, but this doesn't necessarily mean they were accepted by the recipient's mail server or delivered to the inbox. The key to resolving such issues often lies in obtaining detailed SMTP transaction logs, which can pinpoint exactly where the email delivery process failed after leaving your ESP's control. Without these logs, diagnosing the problem becomes significantly more challenging, as safelisting alone does not guarantee inbox placement.
Key findings
- Beyond 'sent': An email being marked 'sent' by your platform, such as Pardot, does not confirm it was accepted by the recipient's mail server. Acceptance is a critical step that indicates the receiving server took possession of the email.
- Log access is vital: Accessing the full SMTP transaction logs (from your ESP and ideally the recipient's server) is crucial to understanding where the email journey ended. This data provides exact timestamps and message IDs.
- Shifting responsibility: If the recipient's server accepted the email, according to RFCs (Request for Comments, the internet standards for email), the responsibility for delivery or notification of non-delivery shifts to their system. Pinpointing this handoff is key.
- Safelisting limitations: While safelisting helps, it doesn't guarantee emails won't be filtered by internal security solutions, user-defined rules, or simply routed to a junk/promotions folder within the recipient's system, even if a blocklist (or blacklist) is not involved.
Key considerations
- Leverage ESP support: Reach out to your email service provider's support team to request detailed SMTP transaction logs for the specific emails in question. Many ESPs do not expose this level of detail in their standard user interfaces.
- Conduct targeted tests: Send a single, unique test email directly to the affected customer's email address. This creates a very specific log entry that is easier for both your ESP and the recipient's IT to trace.
- Collaborate with recipient IT: Provide the customer's IT team with the precise timestamps, sender IP, and message IDs from your ESP's logs. This data enables them to search their inbound mail logs and identify what happened to the email after their server accepted it. This collaboration is crucial for troubleshooting complex deliverability issues.
- Check client-side rules: Encourage the customer to check their spam or junk folders, and to investigate any custom inbox rules they might have set up that could be diverting your emails, even after safelisting.
What email marketers say
Email marketers frequently encounter scenarios where emails are reported as 'sent' by their platform, yet fail to reach the intended recipient's inbox. This common challenge underscores the limitations of basic ESP reporting and the necessity of deeper investigation. Marketers often find themselves needing to go beyond standard metrics to confirm email acceptance and navigate the complexities of recipient-side filtering, even when domains are supposedly safelisted. The focus often shifts to understanding the specific journey of an email after it leaves the sender's infrastructure, requiring cooperation from both the ESP and the recipient's IT department. A common theme is the need to trace accepted emails effectively, as safelisting itself may not prevent all forms of filtering.
Key opinions
- Limited ESP insights: Many marketing automation platforms, like Pardot, offer limited visibility into the actual SMTP transaction, only confirming that an email was 'sent' rather than 'accepted' by the receiving server.
- Acceptance is key: Marketers frequently emphasize the distinction between an email being 'sent' and it being 'accepted' by the recipient's mail server, the latter being the crucial confirmation needed for troubleshooting.
- Involve ESP support: The consensus among marketers is to engage their ESP's support team to gain access to the deeper, more technical logs that are typically unavailable through the standard UI.
- Customer IT collaboration: Direct communication with the customer's IT department is seen as essential for providing them with specific message identifiers to trace the email on their end.
Key considerations
- Beyond safelisting: Even with safelisted domains, internal network configurations, security appliances, or user-specific mailbox rules can still prevent emails from reaching the inbox. Understanding these potential blocks is important.
- Targeted sends: Marketers find that sending a single, unique email to the problematic recipient can simplify log analysis due to a smaller, more focused data set.
- Recipient-side filters: It's common for customers to have personal email rules that move messages to different folders or even delete them, even if the domain is globally safelisted by their IT. This is a common aspect when nurturing B2B customers.
- Message tracking IDs: Providing the recipient's IT with specific message IDs and timestamps allows them to trace the email's internal path after it was accepted by their mail server.
Marketer view
Marketer from Email Geeks states they confirmed weekly email sends for 3 months, with Pardot reporting successful delivery, but the customer still claims non-receipt. This highlights a common disconnect between an ESP's 'sent' status and actual inbox placement, indicating a deeper deliverability issue.
Marketer view
Marketer from a marketing forum suggests that even if an email is marked as 'delivered,' it could still be routing to a promotions tab or a junk folder, which users often overlook. This emphasizes the need for recipients to check all possible folders, not just the primary inbox, and for senders to remind them of this possibility.
What the experts say
Deliverability experts consistently highlight the critical importance of gaining access to SMTP transaction logs when troubleshooting emails that seem to disappear post-send. Their opinions converge on the principle that once a receiving mail server issues an acceptance reply (e.g., a 250 OK status), the responsibility for that email shifts to the recipient's domain. Experts also frequently point out that while ESPs confirm sends, the granular detail needed for in-depth troubleshooting often requires direct engagement with their support teams. This scenario often involves navigating the complexities of how different systems handle email once it's accepted and then potentially filtered internally.
Key opinions
- Transaction logs are paramount: Experts universally agree that obtaining the actual SMTP transaction logs is the most crucial step for pinpointing the exact failure point in the email delivery chain.
- Responsibility transfer: If the recipient's domain accepts the email, it officially assumes responsibility for its delivery. At this point, the problem is no longer on the sender's side, according to RFCs.
- ESP limitations: Many ESPs do not provide end-users with sufficient access to detailed SMTP logs or real-time delivery statuses beyond a 'sent' or 'not a bounce' notification.
- Complex troubleshooting: Troubleshooting individual email delivery issues without direct access to both sender and recipient mail server logs is exceptionally challenging.
Key considerations
- Traceable message IDs: Providing the recipient's IT team with unique message IDs and timestamps is essential for them to effectively search their internal mail logs. This forms a core part of how email experts troubleshoot deliverability.
- Internal quarantines: Emails can be accepted by an edge server but then quarantined, discarded, or rerouted internally without generating a non-delivery report (NDR) back to the sender.
- Beyond safelisting: Even with safelisting, receiving systems may apply additional filters based on content, sender reputation (IP or domain blocklist), or other criteria. This means a domain being on a blocklist or blacklist could still impact delivery. For further details, consider what happens when your domain is blocklisted.
- Outsourced services: Recipients using outsourced email security or hosting services (like Proofpoint or Mimecast) may have limited direct access to their own detailed mail logs, complicating troubleshooting.
Expert view
Expert from Email Geeks suggests confirming if Pardot reports emails as accepted by the receiving server, not just 'sent'. This distinction is fundamental for diagnosing email deliverability issues, as acceptance signifies a successful handoff.
Expert view
Expert from Word to the Wise suggests that a common scenario is emails being accepted by the gateway but then getting routed to a quarantine folder that the end-user doesn't regularly check. This highlights the post-acceptance filtering challenges.
What the documentation says
Official email documentation, including RFCs (Request for Comments) that define internet standards, provides the foundational understanding of how email delivery works. This documentation clarifies the stages of email transmission and the responsibilities of sending and receiving mail servers. It underscores that while authentication protocols like SPF, DKIM, and DMARC are crucial for deliverability and preventing your domain from being put on a blocklist or blacklist, they don't preclude internal filtering or user-level rules on the recipient side. The documentation explains that a successful SMTP transaction only confirms acceptance by the receiving server, not guaranteed inbox placement. For instance, even with strong compliance, emails can still face issues, as explored in guides on why emails might go to spam.
Key findings
- SMTP handoff: The SMTP protocol (e.g., RFC 5321) defines a successful email transfer as the receiving server issuing a 250 OK reply, indicating it has accepted responsibility for the message.
- Post-acceptance flow: After acceptance, emails typically undergo further processing, including spam and malware scanning, transport rules, and routing by a local delivery agent (LDA), which can lead to diverse outcomes like inbox placement, quarantine, or junk folder delivery.
- No inbox guarantee: While authentication (SPF, DKIM, DMARC) and safelisting are crucial, official documentation implies they improve deliverability, but do not guarantee an email will bypass all internal filters or land in the primary inbox. Refer to a simple guide to DMARC, SPF, and DKIM.
- NDR expectation: If an email is accepted but cannot be delivered to the final mailbox (e.g., due to a non-existent user), the receiving server is expected to issue a Non-Delivery Report (NDR) back to the sender.
Key considerations
- Log analysis: Understanding SMTP response codes (e.g., 2xx for success, 4xx for temporary failures, 5xx for permanent failures) is key for interpreting mail logs and identifying delivery issues.
- Internal routing: Even within a single organization, emails can be routed through multiple internal systems after initial acceptance, each with its own filtering or redirect rules.
- User-level controls: Many email clients and web interfaces allow individual users to set up personal filtering rules that can override or supplement system-wide configurations, even affecting why emails go to spam.
- Message tracing tools: Many email platforms (e.g., Microsoft 365, Google Workspace) provide message tracing tools for administrators to follow an email's path post-acceptance.
Technical article
Documentation from RFC 5321 states that a successful SMTP transaction concludes when the receiving server issues a 250 OK reply, indicating it has accepted responsibility for the message. This acceptance is a crucial point where the email's fate transitions to the recipient's system.
Technical article
Technical guide from Microsoft Exchange documentation explains that even after initial acceptance, emails are subject to transport rules, spam filters, and malware checks within the recipient's system. These internal processes can reroute or block messages before they reach the inbox.
Related resources
4 resources
Related pages
How to determine if marketing emails are going to spam?
What to do when emails are blocked by major ISPs despite passing DMARC, SPF, DKIM?
Why are emails not being received by a B2B client with no bounce errors?
How to improve B2B email deliverability and avoid spam folders when nurturing customers?
How to troubleshoot emails landing in spam despite passing DKIM, SPF, and DMARC?
Why Your Emails Are Going to Spam in 2024 and How to Fix It
What happens when your domain is on an email blacklist?
A simple guide to DMARC, SPF, and DKIM
How email blacklists actually work: a simple guide
A practical guide to understanding your email domain reputation
