Understanding SPF, DKIM, and How They Work with DMARC and Alignment FOR NERDS!!!
SPF (Sender Policy Framework)
SPF is like an access control list for email servers. It’s a DNS (Domain Name System)
record that specifies which IP addresses are allowed to send emails on behalf of your
domain. When an email is sent, the receiving server checks the SPF record to verify
if the sender’s IP address matches the ones authorized to send for that domain. If
it doesn’t match, the email is flagged or rejected. This helps to reduce email
spoofing, where attackers try to pretend to be someone they’re not.
DKIM (DomainKeys Identified Mail)
DKIM is all about authenticity. It adds a digital signature to your emails using
cryptographic keys, which are stored in your DNS. When your email is sent, it’s
signed with a private key; the receiving server then checks this signature against
the public key in your DNS record to verify that the email hasn’t been tampered with
in transit. It’s like a tamper-evident seal, ensuring the content remains unaltered
from sender to receiver.
DMARC (Domain-based Message Authentication, Reporting, and Conformance)
DMARC sits on top of SPF and DKIM as the policy enforcer. It tells receiving email
servers what to do if an email fails the SPF or DKIM checks—like quarantine or reject
the message. DMARC also provides reporting, so you can see who’s sending on behalf
of your domain, giving you visibility into any unauthorized senders. The real power
of DMARC comes with its alignment feature.
Alignment and How It Works
Alignment in DMARC is what ties SPF and DKIM together. It checks if the domains used
in SPF and DKIM match the domain in the "From" address of the email. There are two
types of alignment:
- Strict Alignment: The domain must match exactly.
- Relaxed Alignment: The domains must be organizationally the same,
meaning subdomains are acceptable.
Alignment ensures that an email isn’t just technically correct with SPF and DKIM but
also visually and contextually aligns with your domain, further protecting against
impersonation attacks.
How They Work Together
Think of SPF, DKIM, and DMARC as layers of a security fence. SPF checks who’s
allowed in, DKIM ensures the message hasn't been tampered with, and DMARC sets the
rules and monitors everything. Proper alignment of these protocols creates a
stronger barrier against phishing, spoofing, and other email-based threats,
enhancing your domain's security posture.
TLDR; SPF and DKIM help prove the email is legit, and DMARC, with its alignment
checks, makes sure that everything lines up correctly to keep your domain’s
reputation intact.
Sept, 2024
