What is SPF Alignment?
SPF Alignment is the alignment of two (2) headers in an email message, meaning the value found in those two headers(a domain) must align with one another. This alignment means that the value found in each header, which is a domain, must match the domain found in the other header.
SPF checks that the IP address/Domain of the sending server is authorized by the owner of the domain that appears in the SMTP MAIL FROM command. (The email address in MAIL FROM is also called the bounce address, envelope-from, or RFC5321.MailFrom.) In addition to requiring that the SPF check passes, DMARC checks that RFC5321.MailFrom aligns with 5322.from.
Example:
An email is sent with a From address of abc@example.com and the Return Path is mail.example.com. In this case, the email is considered to be SPF-aligned.
An email is sent with a From address of abc@example.com. and the Return Path is mail.dmzv.com. In this case, the email is not aligned.