DMARC aspf= Tag — SPF Alignment (aspf)

The DMARC aspf tag controls how strictly the SPF envelope-from domain must match the From header domain. "r" allows subdomain matches; "s" requires exact match.

Importance
Optional
Tag
aspf=
Default
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.

📚 RFC References

↗RFC 7489 §3.1 — Identifier Alignment

🔗 Related DMARC Tags

adkim=
DKIM Alignment (adkim)

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