How to troubleshoot spam placement issues with a third-party vendor using SendGrid?

Key findings

• SPF validation: SPF (Sender Policy Framework) checks against the Return-Path (or Envelope-From) domain, not the From (or friendly From) header. SendGrid typically sends via a branded subdomain for the Return-Path, and the SPF record for this subdomain is managed by SendGrid, not necessarily needing an explicit entry in your main domain’s SPF.
• DKIM alignment: DKIM (DomainKeys Identified Mail) is verified against the header.d domain, which should align with your From domain for DMARC alignment. SendGrid usually provides CNAME records for DKIM authentication, linking your domain to their sending infrastructure.
• DMARC policy: A DMARC policy (e.g., p=quarantine) instructs receiving mail servers on how to handle emails that fail DMARC authentication checks. While beneficial for security, it relies on proper SPF and DKIM alignment by the sending service. You can learn more about DMARC, SPF, and DKIM in our detailed guides.
• IP reputation: Spam folder placement is frequently tied to the reputation of the sending IP address. If the third-party vendor's SendGrid dedicated IP has a poor reputation, or if it's a shared IP with other senders engaged in problematic practices, emails may be flagged as spam regardless of authentication. Monitoring your email domain reputation is crucial.
• Content and engagement: Even with perfect authentication, poor email content (spammy keywords, suspicious links), low engagement rates, or high spam complaint rates can trigger spam filters.

Key considerations

• Verify SendGrid setup: Ensure your third-party vendor has correctly set up domain authentication in SendGrid, including both SPF and DKIM records for the subdomain used as the Return-Path.
• Analyze email headers: Obtain full email headers from a spam-placed message. Look specifically at the Authentication-Results header to confirm SPF, DKIM, and DMARC passes, and identify the smtp.mailfrom domain.
• Monitor deliverability: Regularly check SendGrid's deliverability dashboards, spam complaint rates, and blocklist (or blacklist) status for their sending IPs. Understand how to diagnose email deliverability issues.
• Review sending practices: Work with the vendor to ensure their sending practices align with email best practices, including list hygiene, consent management, and content optimization to reduce spam complaints.

Key opinions

• SPF confusion: Many marketers initially believe adding an include statement for the vendor's main domain (like sendgrid.net) to their SPF record will solve spam issues, but this is often incorrect if the vendor uses a branded subdomain for the Return-Path.
• Subdomain importance: There's a strong consensus that third-party vendors, especially ESPs, should set up proper domain authentication using branded subdomains (e.g., em.yourdomain.com) for their clients to ensure SPF and DKIM align correctly with DMARC.
• ESP reputation concerns: Some marketers express concern over the general reputation of certain large ESPs (like SendGrid), suggesting that their shared IP pools can lead to deliverability challenges despite correct authentication. This can lead to emails going to spam even with proper setup.
• Beyond authentication: While authentication is crucial, marketers recognize that spam folder placement isn't solely due to DMARC, SPF, or DKIM. IP reputation and content filters are also major contributing factors, requiring a holistic approach to deliverability. Read more about why your emails might be going to spam.

Key considerations

• Educate IT teams: Marketers often need to bridge the knowledge gap between their marketing efforts and the technical understanding of IT teams regarding email deliverability, especially when dealing with third-party vendors and complex DNS records.
• Review authentication headers: When troubleshooting, always check the Authentication-Results header of a problematic email to see which domains are being checked for SPF and DKIM. This is vital for understanding what's happening. You can also explore how to troubleshoot emails landing in spam despite passing authentication.
• Push for branded mail from: Encourage third-party vendors to set up branded mail from domains (custom return paths) to ensure proper SPF alignment and stronger brand identity.
• Focus on data and content: If authentication checks pass, attention should shift to the quality of registration data and whether users are misusing the platform to send unsolicited emails, which can significantly damage the sending reputation.

Key opinions

• SPF validation specifics: Experts agree that SPF validates the smtp.mailfrom (or Return-Path) domain, not the From header. Therefore, adding a vendor's general domain to your main SPF record is often unnecessary if the vendor uses a properly authenticated subdomain for the Return-Path.
• DKIM's role in alignment: While SPF checks the Return-Path, DKIM is typically checked against the From domain. For DMARC alignment, either SPF or DKIM must align with the From domain. SendGrid facilitates this via CNAME records.
• Root cause beyond authentication: Even when SPF, DKIM, and DMARC pass, experts frequently attribute spam folder placement to factors like IP reputation (especially with shared IP pools from large ESPs) and content quality. For instance, Spam Resource highlights the critical role of IP reputation.
• User behavior impact: Experts stress the importance of monitoring how customers or users interact with the third-party platform. If some users are sending unsolicited email via the platform, this can generate spam complaints that harm the overall sending reputation, causing legitimate emails to be blocklisted or sent to spam.

Key considerations

• Header analysis: The first step in troubleshooting is always to examine the full email headers, specifically the Authentication-Results to identify which domains passed SPF and DKIM, and confirm DMARC alignment. This is key to understanding the authentication chain. You can also review our guide on why your emails go to spam.
• Branded sending domains: Ensure the third-party vendor has set up a branded sending domain (with custom Return-Path) for your emails. This improves sender authentication and brand consistency, crucial for inbox placement. This is explained further in the Twilio SendGrid Deliverability Guide.
• Audit registration data: Investigate the overall registration data to see if there are any patterns of unsolicited email sending by customers or users of the platform, as this directly contributes to reputation damage and spam complaints. This could indicate a need for stricter onboarding processes.
• Monitor blocklists (blacklists): Regularly check if the sending IP (or IP range) used by the third-party vendor is listed on any common DNS blocklists or blacklists. Such listings can immediately push emails to the spam folder. Understanding how email blacklists work is important.

Key findings

• Domain authentication setup: SendGrid's documentation provides a comprehensive guide on how to set up domain authentication, including SPF and DKIM records, to improve deliverability and security. This involves adding CNAME records to your DNS.
• SPF and DKIM verification: Technical documentation clarifies that SPF validates the Return-Path domain, while DKIM verifies the message content and associates it with the header.d domain, which typically aligns with the From domain.
• DMARC alignment: DMARC requires either SPF or DKIM to align with the From domain. If these checks pass, emails should pass DMARC, indicating the problem might lie elsewhere if emails still go to spam.
• Proactive monitoring: Official guides, like the Twilio SendGrid Support Deliverability Guide, advise proactive monitoring of sender reputation, spam complaints, and blocklists (blacklists) to address deliverability issues promptly.

Key considerations

• DNS configuration: Carefully follow the ESP's documentation for adding the correct CNAME records to your DNS. These records are essential for delegating sending authority to the third-party vendor and ensuring proper authentication.
• Review Authentication-Results: When troubleshooting, always examine the Authentication-Results header in a received email. This header provides clear feedback on the outcome of SPF, DKIM, and DMARC checks, helping to pinpoint authentication failures.
• Spam complaint handling: Documentation often emphasizes the importance of managing spam complaints. High complaint rates can lead to throttling or blocklisting, even with proper authentication. SendGrid has specific guidelines on dealing with spam complaints.
• Blocklist (blacklist) monitoring: Pay attention to alerts regarding IP addresses being listed on blocklists (blacklists) like UCEPROTECT, even if using a major ESP. Documentation, like SendGrid's article on UCEPROTECT Blocklistings, explains how these can affect deliverability.