Why are Comcast customers not receiving password reset emails despite logs showing successful delivery?

Key findings

• Log discrepancy: Emails show as successfully delivered in sender logs, but recipients confirm non-receipt, even in spam or trash folders.
• Transactional vs. marketing: The issue specifically affects password reset (transactional) emails, while marketing emails from the same company are received without problems, often even when sent from the same IP range or domain.
• Comcast's filtering: Comcast's internal filtering policies or anti-spam systems are likely responsible for quarantining or silently dropping these messages post-acceptance.
• Lack of response: Attempts to contact Comcast support or use unblock forms often yield no response or temporary fixes, indicating the problem isn't a straightforward IP blocklist (blacklist) issue.

Key considerations

• Content analysis: Investigate the content of password reset emails for elements that might trigger phishing or spam filters, such as suspicious links, unusual formatting, or generic language. This is particularly relevant when emails are delivered but not received.
• SMTP replies: While logs show 'delivered,' obtaining the exact SMTP replies from Comcast's mail servers, even a 250 OK, might provide hidden IDs or additional context for further investigation.
• Authentication checks: Ensure your DMARC, SPF, and DKIM records are correctly configured and aligned for the sending subdomain. Misconfigurations can lead to silent filtering by ISPs like Comcast. Learn more about DMARC, SPF, and DKIM.
• Recipient commonalities: Look for commonalities among the affected Comcast customers, such as email client, device, or installed antivirus software, which might be locally filtering the emails. The Xfinity Community Forum has discussions on password reset email issues.

Key opinions

• Delivery confirmation: Many marketers find their ESP logs confirm successful delivery, yet customers report not receiving emails, which suggests an internal filtering issue at the recipient's end.
• Different subdomains: Some marketers are hesitant to send sensitive transactional emails, such as password resets, from marketing subdomains, especially if the problem is localized to specific ISPs like Comcast. This is because they might encounter issues similar to when transactional emails to Comcast are not received.
• Comcast support: Marketers frequently express frustration with Comcast's unresponsiveness to unblock requests or general deliverability inquiries, leading to a recurring loop of issues.
• Content vs. IP: A common sentiment is that these issues are less about IP blocklisting and more about content or phishing filters, particularly for sensitive email types. For more on this, check out why your emails are going to spam.

Key considerations

• Transactional domain: Maintaining a dedicated subdomain for transactional emails is a good practice, but it's crucial to ensure its deliverability for critical messages like password resets.
• Alternative delivery: Consider implementing alternative methods for password resets, such as in-app notifications, to mitigate reliance on email for critical functions.
• Customer feedback: Encourage customers to check all folders, including junk and trash, and to whitelist your sending address, even if they report having done so.
• Persistent monitoring: Despite a lack of direct responses, continue to monitor and log all communication attempts with Comcast's delivery support to build a case for persistent issues. Vocal Media shares some fixes for common Comcast email issues.

Key opinions

• Beyond IP blocks: Experts generally agree that if mail is reported as delivered, the issue is not with IP blocklisting, but rather content filtering or phishing detection. This falls under common email blacklist workings.
• Content is key: Sensitive emails like password resets are prone to content or phishing filters. Changing content or sending domain can help diagnose this.
• Trust logs, verify reception: If an MTA (Mail Transfer Agent) reports delivery, the mail was likely accepted, but acceptance doesn't guarantee inbox placement.
• Authentication check: DMARC misconfigurations or authentication issues can lead to silent email failures, warranting a thorough review.
• ISP internal policies: ISPs like Comcast have their own anti-spam policies, which can override general filtering hints from third-party services like Vade Secure.

Key considerations

• Verify SMTP logs: Always ensure that delivery logs reflect actual SMTP replies from the receiving ISP, not just internal application confirmations. This can help prevent issues such as when emails are not received by a B2B client.
• Contact ISP support: Directly engage Comcast's delivery support (e.g., Delivery-Support@cable.comcast.com) with specific examples and full SMTP replies.
• Test content changes: Experiment with minimal content in password reset emails to see if a specific phrase or link is triggering filters. This is crucial for understanding email deliverability issues.
• Monitor domain reputation: Actively monitor your domain's reputation and any specific blocklists (blacklists) it might appear on, even if it's not the primary issue. SpamResource offers resources on email deliverability.

Key findings

• SMTP acceptance: A '250 OK' SMTP response signifies that the receiving server has accepted the email for processing, but does not guarantee delivery to the inbox.
• Internal filtering: ISPs employ sophisticated internal filtering mechanisms, including spam, phishing, and malware detection, that can move emails to junk folders or silently discard them.
• Authentication validation: Proper SPF, DKIM, and DMARC alignment is critical. Failure in any of these can lead to messages being treated suspiciously, even if initially accepted. This relates to DMARC verification failures.
• Content sensitivity: Emails related to passwords or account security are subject to heightened scrutiny by anti-phishing filters, regardless of sender reputation.

Key considerations

• Maintain reputation: Consistently send desired mail to valid recipients to build and maintain a strong sender reputation across all subdomains and IP addresses. Understanding email domain reputation is crucial.
• Review content policies: Regularly review your email content against known spam triggers and phishing indicators, especially for critical transactional messages.
• Seek ISP postmaster guides: Consult ISP-specific postmaster guides for their recommended best practices and contact channels for delivery issues. Always check for Comcast's guidelines.
• Monitor DMARC reports: Analyze aggregate and forensic DMARC reports to identify authentication failures or unusual mail handling patterns by recipient mail servers.