How do SPF, DKIM, DMARC, and dedicated IPs affect email deliverability when using a third-party ESP?

Key findings

• Authentication impact: SPF and DKIM are fundamental for email authentication, verifying that emails are sent by authorized servers and have not been tampered with. These protocols are critical for establishing trust with receiving mail servers.
• DMARC's role: DMARC builds upon SPF and DKIM, providing instructions to mailbox providers on how to handle emails that fail authentication. It also offers reporting capabilities, giving senders insight into their email streams.
• ESP collaboration: Your ESP plays a significant role in supporting these authentication methods, particularly for DKIM signing, and ensuring proper SPF records are in place that include their sending infrastructure. Some ESPs might sign emails using their domain, which can impact DMARC alignment if not configured correctly.
• Dedicated IP considerations: While a dedicated IP can offer more control over your sending reputation, its effectiveness depends heavily on your sending volume and practices. For low-volume senders, a shared IP (managed well by an ESP) might be more beneficial. A dedicated IP also requires a proper IP warming process.
• Troubleshooting methodology: When facing deliverability issues, identifying the specific mailbox providers or recipient types (e.g., Gmail, corporate domains, educational institutions) where emails are going to spam is the critical first step. Solutions often vary depending on the destination.

Key considerations

• Domain alignment: Ensure your SPF and DKIM records align with your sending domain, not just the ESP's domain. This is crucial for DMARC to pass.
• Content and engagement: Beyond technical setup, the quality of your email content, subscriber engagement, and list hygiene are paramount. These factors often outweigh the impact of IP type.
• ISP-specific rules: Different Internet Service Providers (ISPs) have varying spam filtering algorithms and policies. What works for Gmail might not work for a private corporate domain. Understanding these nuances is vital.
• Reporting and feedback loops: Utilize DMARC reports and ISP feedback loops to gain insights into your email performance and identify potential issues. For more details on authentication, refer to this Klaviyo guide on email authentication.

Key opinions

• ESP authentication support: Many ESPs, like Recurly, offer SPF and DKIM signing, which contributes to better deliverability. However, the critical detail is whether they sign with your domain or their own, which can affect DMARC alignment.
• Domain vs. ESP signing: Marketers frequently encounter situations where an ESP supports signing on their own domain, but not directly on the client's domain, leading to authentication challenges when sending from their own domain.
• Dedicated IP effectiveness: There's often debate among marketers about whether a dedicated IP truly improves deliverability, especially if core authentication (like DKIM with one's own domain) isn't fully in place or if other factors like content are the primary issue.
• Target audience challenges: Marketers recognize that certain recipient domains, such as schools, universities, or highly restrictive enterprise networks, often have very strict email filtering policies, making them inherently harder to reach.

Key considerations

• Prioritize problem identification: Before exploring technical solutions like dedicated IPs or advanced authentication, the most crucial step is to pinpoint exactly where emails are failing to be delivered (e.g., Gmail, specific business domains).
• Verify ESP capabilities: Thoroughly investigate your ESP's documentation and support to understand their full capabilities for SPF, DKIM, and DMARC with your specific sending domain. This might involve setting up custom DNS records.
• Holistic deliverability view: Deliverability is rarely a single-point failure. Consider all contributing factors, including email content, subscriber engagement, list quality, and even how your transactional emails are classified by recipients. For more insights on overall deliverability, check out Salesforce's guide to email deliverability.

Key opinions

• DMARC's direct impact: Experts suggest that DMARC may have only a marginal effect on deliverability if you are already using your own domain with proper SPF and DKIM. Its primary role is in reporting and policy enforcement rather than direct delivery improvement.
• SPF and DKIM sufficiency: If you use your own domain, the ESP's main role for DMARC is to support proper SPF and DKIM implementation. If these are correctly configured, you might already have a strong foundation.
• Dedicated IP debate: There's skepticism among experts about the universal benefit of dedicated IPs. For some senders, particularly those dealing with major mailbox providers like Gmail, a dedicated IP might not offer significant deliverability advantages and could even hinder delivery during the warming period.
• Content over IP: If SPF is correctly set up, deliverability problems are often more likely related to email content, links within the message, or how recipients interact with your emails, rather than the IP address itself.

Key considerations

• Diagnostic approach: The first and most crucial step in troubleshooting is to precisely identify which ISPs or domains your mail is going to spam at. The resolution strategy differs significantly for Gmail versus private business or educational domains. Without this data, troubleshooting is like guessing.
• DKIM alignment for DMARC: While you can set up a DMARC policy of p=none, implementing stricter policies like p=quarantine or p=reject is not advisable unless you have the ability to sign DKIM with your own domain (d=yourdomain.com).
• Recipient-specific challenges: Transactional emails sent to businesses, enterprises, or educational institutions often face stricter filtering. A dedicated IP may not overcome these hurdles, and a targeted approach based on recipient type is usually needed. Read more on the value of DMARC at Mailgun's DMARC Explained.

Key findings

• Authentication necessity: Messages require passing DKIM and SPF alignment checks to be delivered, as dictated by DMARC policies. This highlights the interconnectedness of these protocols for successful email delivery.
• DMARC's protective function: DMARC policies are designed to protect your domain from being spoofed by unauthorized third parties. They instruct ISPs to reject or quarantine emails that fail authentication and attempt to use your domain in the From header.
• SPF for reputation: Implementing SPF records is crucial for improving email deliverability and protecting your domain's reputation by reducing the chances of your emails being flagged as spam.
• DMARC insights: Unlike SPF and DKIM, DMARC provides senders with valuable insights into their deliverability performance through reports, regardless of the chosen policy (e.g., p=none, p=quarantine, p=reject).

Key considerations

• Comprehensive authentication: Authentication protocols (SPF, DKIM, and DMARC) add crucial layers of security, which directly contribute to maintaining a positive sender reputation and, by extension, better deliverability. It is important to safeguard your reputation at all costs, and sender reputation plays a critical role in inbox placement.
• DMARC policy options: When setting up DMARC, different policies (none, quarantine, reject) suggest how emails failing SPF or DKIM authentication should be filtered, offering flexibility in enforcement.
• Beyond authentication: While authentication is foundational, it's part of a broader email deliverability checklist. Other factors, such as list hygiene, content quality, and engagement, are equally vital for consistent inbox placement. Check your DMARC records with this guide to SPF records.