Summary
The issue of login verification emails not being received despite logs showing delivery is complex, involving factors on both the sending and receiving ends, as well as content and authentication issues. Experts and marketers emphasize checking MTA logs, recipient-side spam filters and configurations, and MX records to identify filtering systems. Content triggering spam filters, poor sender reputation, lack of user engagement, greylisting, delayed filtering rules, suppression lists, authentication problems (SPF, DKIM, DMARC), blocklisting, and custom recipient filters all contribute to this problem. Proactive measures such as seedlisting, maintaining a clean email list with explicit permissions, and carefully monitoring sender reputation are essential for ensuring reliable delivery.
Key findings
- MTA Logs are Critical: The first step is always to check the MTA logs to verify the message was sent and accepted. These logs may contain details of any error or failure.
- Recipient-Side Issues are Common: Recipient-side configurations (spam filters, client settings), as well as server-side policies, can prevent emails from being received despite delivery.
- Content Matters: Email content can trigger spam filters, regardless of delivery logs. Check for spam triggers, insecure elements, and improper formatting.
- Reputation is Key: Sender IP and domain reputation significantly impact deliverability. Poor reputation can lead to filtering or delays.
- Authentication is Crucial: Proper authentication (SPF, DKIM, DMARC) is critical to avoid being marked as spam. Verify your setup.
- Permissions Prevent Problems: Obtaining explicit permission from recipients is essential. Sending unsolicited emails can result in deliverability issues.
- List Management is Essential: Suppression lists, inactive users, and bounce rates negatively impact deliverability. Manage lists actively.
- Seedlisting Helps Diagnose: Proactive seedlisting identifies deliverability issues before widespread sending.
- Greylisting Can Delay Delivery: Greylisting (temporary rejection) can delay emails if the sending server does not retry.
Key considerations
- Review MTA Logs: Begin troubleshooting by checking the MTA logs for detailed delivery information.
- Analyze Recipient MX Records: Examine the recipient's MX records to identify which mail service or spam filter is being used.
- Perform Inbox Placement Tests: Conduct inbox placement tests to assess how your emails are being filtered by different providers.
- Monitor Sender Reputation: Continuously monitor your IP and domain reputation and address any negative feedback loops.
- Optimize Email Content: Refine email content to avoid spam triggers. Ensure proper HTML formatting and remove insecure elements.
- Verify Authentication Setup: Confirm that SPF, DKIM, and DMARC records are correctly configured and valid.
- Manage List Hygiene: Maintain clean lists, remove inactive users, and handle bounces promptly to reduce deliverability issues.
- Implement Seedlisting: Incorporate seedlisting to test and monitor inbox placement before each mailing.
- Obtain User Consent: Always obtain explicit permission from recipients before sending emails to comply with regulations and improve deliverability.
- Check Recipient-Side Filters: Advise recipients to check their spam/junk folders, and to whitelist the sending domain if necessary.
What email marketers say
15 marketer opinions
Even when login verification emails are shown as delivered in logs, various factors can prevent recipients from actually receiving them. These factors span the sending server, the receiving server, the content of the email, and recipient-specific configurations. Issues range from greylisting and delayed filtering rules to content triggering spam filters, poor sender reputation, and recipient-side customizations like custom filters or accidental unsubscribes. Checking authentication (SPF, DKIM, DMARC), monitoring IP and domain reputation, reviewing MX records, engaging content, and ensuring proper list management and permissions are critical for ensuring deliverability.
Key opinions
- MTA Logs: The first step is always to check the MTA's send logs to verify that the message was sent and accepted by the receiving server.
- Recipient Server Policies: Recipient servers may have specific policies based on reputation, content, or sender behavior that lead to quarantining or delaying emails, despite initial successful delivery.
- Content-Related Filtering: Email content can trigger spam filters on the recipient's end, regardless of authentication. Review content for spam triggers, insecure elements, and proper formatting.
- Suppression Lists: Recipients may have accidentally unsubscribed or been added to a suppression list, blocking further emails.
- Delayed Filtering Rules: Filtering rules on the receiving server may not be applied immediately, leading to a delay in how messages are processed.
- Authentication Issues: Problems with SPF, DKIM, and DMARC can cause emails to be marked as spam even if delivered to the server. Verify authentication setup.
- IP Reputation: Low IP reputation can cause recipient servers to filter or delay emails, despite successful initial delivery.
- Custom Filters: Recipients may have custom filters that override global spam settings, catching login verification emails.
- Blocklists: The sending IP or domain may be on email blocklists, preventing delivery.
Key considerations
- Check MTA Logs: Always start by examining the MTA's send logs to confirm that the message was indeed sent and accepted.
- Review Recipient's MX Records: Check the MX records for the custom domains to identify which mail service or spam filter is in use and any commonalities among affected recipients.
- Inbox Placement Tests: Conduct inbox placement tests to see if any mailbox providers or spam filters are flagging the emails.
- Monitor Sender Reputation: Regularly monitor your sender reputation to identify and address any issues that might affect deliverability.
- Optimize Email Content: Carefully review email content to avoid common spam triggers and ensure proper formatting and secure elements.
- Manage Suppression Lists: Regularly review suppression lists to ensure users aren't accidentally blocked.
- Verify Authentication: Ensure that SPF, DKIM, and DMARC records are properly configured and validated.
- List Management: Practice diligent list management, ensuring explicit permissions and minimizing spam complaints.
Marketer view
Email marketer from Email Geeks suggests doing an inbox placement test and a deep dive on metrics for the specific mail stream. If the content is different, it might be the issue, so check for insecure elements (HTTP instead of HTTPS) and ensure images are losslessly compressed.
15 Feb 2024 - Email Geeks
Marketer view
Email marketer from Email on Acid advises ensuring your sending IP or domain isn't on any email blocklists, which can cause delivery issues despite logs showing successful sending.
16 Jul 2023 - Email on Acid
What the experts say
5 expert opinions
Experts suggest a multi-faceted approach to address the issue of login verification emails not being received despite logs showing delivery. This involves scrutinizing delivery details from the sending platform (ideally including a three-digit number, peer IP address, and timestamp), examining recipient MX records, proactively testing inbox placement with seedlisting, verifying DNS records to prevent authentication failures, and continuously monitoring sender reputation as a critical factor influencing email placement.
Key opinions
- Delivery Details Importance: Obtaining granular delivery details (status code, IP, timestamp) from the sending platform is crucial for diagnosing issues beyond basic 'delivered' status.
- MX Record Examination: Analyzing recipient MX records helps identify the specific mail service or spam filter in use, enabling targeted troubleshooting.
- Proactive Seedlisting: Using seedlists to test inbox placement before large-scale sending can reveal deliverability problems not apparent in logs.
- DNS & Authentication: Underlying DNS issues can lead to authentication failures (SPF, DKIM, DMARC), causing deliverability problems even with successful sending.
- Sender Reputation Matters: Sender reputation significantly impacts email placement; a poor reputation may result in emails being filtered despite technical delivery.
Key considerations
- Request Detailed Logs: Request comprehensive delivery logs from your email sending platform, looking for status codes, IP addresses, and timestamps.
- Analyze Recipient Infrastructure: Investigate the recipient's email infrastructure by examining their MX records to identify potential filtering systems.
- Implement Seedlisting: Incorporate seedlisting into your email sending process to proactively monitor and address inbox placement issues.
- Regular DNS Checks: Periodically review your DNS records to ensure proper authentication configurations and prevent authentication failures.
- Monitor Sender Reputation: Actively monitor your sender reputation and take steps to improve it to enhance email deliverability.
Expert view
Expert from Spam Resource explains that DNS issues can cause authentication failures (SPF, DKIM, DMARC) that might not be immediately obvious but lead to deliverability problems. Suggests carefully reviewing DNS records.
24 Sep 2021 - Spam Resource
Expert view
Expert from Spam Resource discusses Seedlisting to test inbox placement with real accounts before sending. This proactive approach can help identify if emails are landing in spam folders despite showing as delivered.
28 Apr 2023 - Spam Resource
What the documentation says
4 technical articles
Documentation from various sources indicates that even if logs show successful delivery of login verification emails, the recipient's mail server and client configurations play a crucial role in whether the email reaches the intended inbox. Aggressive spam filters, incorrect client configurations, filtering to less obvious folders (like junk or quarantine), and invalid DKIM signatures can all lead to delivery failures despite a successful SMTP transaction. A complete delivery process involves policies and configurations beyond the basic SMTP protocol.
Key findings
- Recipient-Side Filtering: Aggressive spam filters and incorrect email client configurations on the recipient's side can prevent emails from reaching the inbox.
- Non-Inbox Folders: Emails may be routed to less obvious folders like junk or quarantine, even with successful delivery.
- SMTP Guarantee: A successful SMTP transaction does not guarantee inbox delivery; recipient servers can filter emails post-acceptance.
- DKIM Validity: Invalid DKIM signatures can cause emails to be marked as suspicious or sent to the junk folder.
Key considerations
- Check Recipient Filters: Advise recipients to check their spam filters, email client configurations, and other folders for missing emails.
- Implement Robust DKIM: Ensure proper implementation and verification of DKIM signatures to avoid emails being marked as suspicious.
- Understand SMTP Limitations: Recognize that a successful SMTP transaction is not a guarantee of final delivery; consider other factors beyond the SMTP protocol.
- EOP Check: If using Microsoft Exchange Online Protection, advise recipients to check their Junk and Quarantine folders.
Technical article
Documentation from Microsoft explains that Exchange Online Protection can accept a message but still filter it post-delivery, moving it to junk or quarantine. It suggests checking these locations if the logs indicate successful delivery.
1 May 2025 - Microsoft
Technical article
Documentation from RFC Editor (specifically RFC 5321 on Simple Mail Transfer Protocol) explains that successful SMTP transaction doesn't guarantee inbox delivery. Recipient server can accept the message and later discard or filter it. Full delivery involves policies beyond the basic SMTP protocol.
24 Jul 2022 - RFC Editor
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