Mailchimp DMARC Alignment — Getting It Right

Sending emails through third-party services like Mailchimp is a standard practice for marketing and transactional communications. However, ensuring these emails pass DMARC alignment checks is a common challenge for many organizations, leading to deliverability issues and a damaged sender reputation. This article will break down how DMARC alignment works with Mailchimp and provide concrete steps to get it right.

Understanding DMARC Alignment (A Quick Refresher)

DMARC (Domain-based Message Authentication, Reporting, & Conformance) is an email authentication protocol designed to protect your domain from impersonation and phishing. It builds upon two foundational authentication methods: SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail).

For DMARC to pass, at least one of SPF or DKIM must "pass" and be "aligned" with the From domain shown to the user.

  • SPF Alignment: This occurs when the domain in the Return-Path header (also known as the "envelope sender" or "mfrom") either exactly matches (strict alignment) or shares the organizational domain with (relaxed alignment) the domain in the From header.
  • DKIM Alignment: This occurs when the d= tag within the DKIM-Signature header either exactly matches (strict alignment) or shares the organizational domain with (relaxed alignment) the domain in the From header.

If neither SPF nor DKIM aligns, the email fails DMARC. Depending on your DMARC policy (p=none, p=quarantine, or p=reject), this can lead to messages being delivered to spam, quarantined, or outright rejected.

Mailchimp and DMARC: The Default Behavior

When you send emails through Mailchimp without any specific domain authentication, here's what typically happens:

  • From Header: You configure this to be your domain, e.g., marketing@yourdomain.com.
  • Return-Path Header: Mailchimp will set this to one of its own domains or a subdomain, such as bounces.mailchimp.com or mcsv.net.
  • DKIM-Signature Header: Mailchimp will sign the email, but the d= tag in the signature will typically be mailchimp.com or mcsv.net.

In this default scenario, both SPF and DKIM will fail alignment:

  • SPF Alignment Failure: The Return-Path domain