DMARC aspf= Tag: SPF Alignment (aspf)
The DMARC aspf tag controls how strictly the SPF MAIL FROM domain must match the From header domain. "r" allows subdomain matches; "s" requires exact match.
Importance
Optional
Optional
Tag
aspf=
Default
r (relaxed)
r (relaxed)
Example
aspf=r
✅ Valid Values
r
Relaxed (default). Organisational domain matching. Subdomains align with parent.
s
Strict. The SPF envelope-from domain must exactly match the From header domain.
💬 What This Tag Does
The "aspf" tag controls how strictly DMARC compares the SPF envelope-from (SMTP MAIL FROM) domain with the email's From header domain. Relaxed mode allows organisational domain matching. Strict mode requires an exact match. Most deployments use relaxed alignment to accommodate bounce addresses and subdomains. Note: RFC 9989 (DMARCbis) uses MAIL FROM only for SPF alignment. The HELO fallback allowed in RFC 7489 has been removed.
📚 RFC References
🔗 Related DMARC Tags
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