Why are SFMC emails showing as delivered but not received by the subscriber?

Key findings

• Post-acceptance filtering: Many business-to-business (B2B) mail servers, and to a lesser extent some consumer-facing providers like Yahoo, may accept an email for delivery, providing a 250 OK SMTP reply, only to then quarantine or discard it due to internal filtering rules, security policies, or user-specific settings. This explains why SFMC sees it as delivered.
• Recipient-side configuration: Individual email recipients might have personal inbox rules, forwarding setups, or highly aggressive spam filters that divert or delete emails without notifying the sender or returning a bounce. This is particularly true if it's an isolated issue affecting only one subscriber.
• Discrepancy in 'delivered' definition: The term 'delivered' from an ESP like SFMC typically means the receiving server acknowledged receipt of the email. It does not guarantee inbox placement, as subsequent internal processing by the recipient's mail system can still affect its final destination.
• Impact on Yahoo deliverability: While Yahoo Mail generally aims to avoid outright discarding emails, issues can arise, especially if sender reputation is impacted. For broader Yahoo deliverability challenges, contacting their postmaster team is a necessary step. You can also explore specific reasons for Yahoo Mail deliverability issues.

Key considerations

• Examine SMTP replies: Although SFMC might show 'delivered,' reviewing the raw SMTP logs (if accessible) can provide deeper insight. A 250 OK response usually means the email was accepted, but some mail servers might return more specific codes indicating soft failures or deferrals.
• Audience segmentation: Distinguish between individual subscriber issues and widespread domain-specific problems. A single non-receipt could be a personal email client setting, while broad non-receipt to a specific domain (like a B2B client's domain) suggests a systemic filtering problem at that organization.
• Recipient engagement: While SFMC reports delivery, monitor opens and clicks closely. A low or zero open rate for 'delivered' emails is a strong indicator of inbox placement issues, even if bounces are not occurring. For further reading, understand why emails aren't appearing in the inbox.
• Communication with recipients: Encourage affected subscribers or B2B clients to check their junk folders, spam filters, or IT department for any specific email filtering rules. Ask them to whitelist your sending domain.

Key opinions

• Internal B2B filtering: Many marketers note that B2B organizations are notorious for accepting emails and then silently dropping or quarantining them due to their stringent internal security and spam filtering systems, often without generating a bounce.
• Yahoo's inbox placement: While Yahoo Mail usually tries to deliver messages, even to spam, some marketers acknowledge that non-delivery to Yahoo can occasionally occur due to less common or highly specific recipient settings, rather than broad filtering policies.
• Sender reputation impact: A strong sender reputation is crucial. Marketers highlight that poor sender reputation can lead to emails being accepted but then filtered heavily by ISPs. Keeping an eye on your domain reputation is vital.
• Defining 'delivered': Marketers recognize that an ESP's 'delivered' status simply means the email was accepted by the recipient's mail server, not necessarily that it landed in the primary inbox or was even seen by the subscriber.

Key considerations

• Subscriber-specific troubleshooting: If only one or a few subscribers are affected, marketers suggest instructing them to check their personal spam folders, junk mail, and any custom inbox rules. The issue might be on their end rather than a widespread deliverability problem.
• Filtering and security solutions: For B2B clients, inquire about the specific email filtering solutions they use (e.g., Proofpoint, Mimecast) to understand potential post-delivery processing. You may need to ask them to whitelist your sending domain.
• Detailed tracking: Review SFMC's individual email results and tracking data meticulously. While it confirms delivery, analyzing open rates, click-through rates, and specific subscriber status can help identify patterns or isolated incidents indicating inbox placement issues.
• List hygiene: Regularly clean email lists to remove inactive or problematic addresses that might be contributing to deliverability problems, even if they don't explicitly bounce.

Key opinions

• Post-acceptance discard: Experts emphasize that B2B recipients, in particular, often discard or quarantine emails after accepting them for delivery. This means the email is logged as 'delivered' by the sending ESP but never reaches the intended inbox or spam folder.
• Recipient's control: Once a receiving MTA gives a final 250 OK, the message is effectively 'theirs.' The recipient, or their email system, has full discretion over what happens next, including silently discarding the email.
• Yahoo's filtering behavior: While B2B filtering is common, Yahoo Mail is less likely to simply 'throw away' emails. If it occurs at Yahoo, it's often due to specific recipient configurations rather than a broad systemic design, making it a more complex issue to diagnose. Refer to our guide on blacklists Yahoo Mail uses.
• Limited ESP visibility: ESPs like SFMC can only report what the receiving server tells them. They lack visibility into the internal filtering processes that occur after the initial SMTP handoff.

Key considerations

• Granular troubleshooting: Troubleshooting requires detailed information beyond just the 'delivered' status. This includes understanding if the issue affects one recipient or many, specific domains, or if there's any pattern to the non-receipt.
• Identify specific filters: For B2B cases, try to ascertain what email filter or security appliance the B2B customer is using. Knowing this can help in understanding their filtering policies. Our guide on troubleshooting B2B delivery issues can be helpful.
• Postmaster engagement: If broad issues are observed with a specific provider like Yahoo (Verizon Media), engaging directly with their postmaster team via postmaster.verizonmedia.com is the correct next step to get insights into their filtering.
• Understanding SMTP responses: While SFMC simplifies delivery status, understanding the nuances of SMTP replies, such as a 250 OK, is crucial for advanced troubleshooting. This indicates the message was accepted, but not necessarily delivered to the inbox.

Key findings

• SMTP 250 OK: Documentation confirms that a successful SMTP transaction ending in a 250 OK response from the receiving mail server is the basis for an ESP logging an email as 'delivered.' This means the message has been handed off successfully.
• Post-delivery processing: Email is subject to further processing by the recipient's mail system after being accepted. This can include spam filtering, virus scanning, content analysis, and custom user rules that may divert or discard the email without returning a bounce message to the sender.
• Subscriber status vs. inbox: Salesforce Marketing Cloud documentation indicates that a subscriber's status (e.g., active) is distinct from their email's final inbox placement. An email can be 'delivered' to an active subscriber but still not appear in their primary inbox.
• Tracking data interpretation: SFMC tracking provides insights into send, delivered, open, and click rates. Discrepancies between delivered counts and open/click rates can strongly suggest inbox placement issues. More information can be found on accessing SFMC tracking information.

Key considerations

• Absence of bounces: The lack of bounce messages (hard or soft) does not equate to successful inbox placement. Many advanced spam filters and corporate firewalls are designed to avoid generating bounces to prevent backscatter or to provide less information to spammers.
• Recipient server policies: Review public documentation or postmaster guidelines for major ISPs like Yahoo (Verizon Media) or enterprise mail systems, as they often outline their filtering approaches and best practices for senders. You can often find common SMTP codes and their meanings in their docs.
• Email authentication: Ensure proper SPF, DKIM, and DMARC authentication. While not directly causing 'delivered but not received' issues (as emails would likely bounce or be rejected outright without authentication), strong authentication increases trust with receiving servers, reducing the likelihood of post-acceptance filtering into spam or junk. Learn more about DMARC, SPF, and DKIM.
• Engagement data: Official Salesforce documentation on email tracking emphasizes the importance of monitoring engagement metrics. Low engagement despite high delivery rates can be a red flag, prompting deeper investigation into inbox placement rather than just delivery status.