Domain alignment is important for Domain-based Message Authentication, Reporting & Conformance (DMARC) to work properly. Domains out of alignment may cause the DMARC check to fail.
With Sender Policy Framework (SPF) alignment, there is a match between the domains of your email's:
- Mail-From (MFrom) address
- Header From address
The two types of SPF alignment are relaxed alignment and strict alignment. Relaxed alignment is assumed if you don't specify the type of alignment, but you can change your DMARC record to require strict alignment using the aspf tag.
Relaxed alignment
With relaxed alignment, only the root domain of the MFrom address must match the root domain of the Header From address. Relaxed alignment allows a subdomain to be used and still meet the domain alignment requirement.
Examples:
- If your MFrom domain is mail.example.com and your Header From is example.com, your email would pass SPF alignment. (The root domains "example.com" match)
- If your MFrom domain is example.mail.com and your Header From is example.com, your email would not pass SPF alignment. (The root domains "mail.com" and "example.com" do not match)
Strict alignment
With strict alignment, the domain of the MFrom address is an exact match for the domain of the Header From address.
Examples:
- If your MFrom domain is mail.example.com and your Header From is mail.example.com, your email would pass SPF alignment.
- If your MFrom domain is mail.example.com and your Header From is example.com, your email would not pass SPF alignment.
