SPF alignment, as reported by services like Validity, often shows 0% even when SPF passes because the domain used for SPF authentication (the 'MAIL FROM' or envelope sender) doesn't match the domain in the 'From' header. This is a common scenario when using third-party sending services or ESPs (like Mailchimp, Constant Contact, Sendgrid, and Amazon SES) that utilize their own infrastructure and domains for sending on behalf of customers. While SPF can pass based on the ESP's domain, DMARC requires alignment between the authenticated domain and the 'From' header domain to ensure the email truly originates from the claimed sender. DMARC can pass with either SPF or DKIM alignment. If DKIM is used, the DKIM domain also needs to align for DMARC to pass. Solutions involve configuring custom MAIL FROM settings, using a custom return-path, or implementing DKIM to achieve proper alignment.