...
- Alignment of SPF authentication results: SPF is an email authentication protocol that verifies the sender's IP address against a list of authorized sending IP addresses published in the DNS records of the sending domain. The "aspf" tag specifies how the domain specified in the SPF authentication result (retrieved from the "Return-Path" or "MAIL FROM" address) should align with the email's From domain when DMARC policy is evaluated.
- Relaxed vs. Strict alignment: Similar to DKIM alignment, the choice between relaxed and strict alignment affects how strict the DMARC policy enforcement is regarding SPF authentication results. Relaxed alignment allows for more flexibility by matching SPF authentication results against organizational domains (the Parent Domain) or their immediate ancestor subdomains, while strict alignment requires an exact match between the SPF-authenticated domain and the email's From domain.
Considerations: The alignment mode specified by the "aspf" tag can impact DMARC policy enforcement and email deliverability. Choosing the appropriate alignment mode depends on your organization's email authentication practices, SPF implementation, and requirements for DMARC policy enforcement.
...