Understanding SPF, DKIM, and DMARC

The Email Authentication Trinity

Email authentication is crucial in today's threat landscape. Without proper authentication, attackers can easily spoof your domain, sending phishing emails that appear to come from your organization.

SPF: Sender Policy Framework

SPF allows domain owners to specify which mail servers are authorized to send email on their behalf.

How SPF Works

1. You publish an SPF record in your DNS
2. Receiving servers check if the sending IP is authorized
3. If unauthorized, the email may be rejected or marked as spam

SPF Record Syntax

v=spf1 ip4:192.0.2.0/24 include:_spf.calimatic.app -all

• v=spf1: SPF version
• ip4:: Authorized IP addresses
• include:: Include another domain's SPF
• -all: Fail all others (strict)
• ~all: Soft fail (recommended while testing)

DKIM: DomainKeys Identified Mail

DKIM adds a digital signature to your emails, proving they haven't been tampered with in transit.

How DKIM Works

1. Your mail server signs outgoing emails with a private key
2. The public key is published in your DNS
3. Receiving servers verify the signature matches

DKIM Benefits

• Integrity: Proves the email hasn't been modified
• Authentication: Confirms the sender's identity
• Reputation: Helps build domain reputation

DMARC: Domain-based Message Authentication

DMARC ties SPF and DKIM together, telling receivers what to do when authentication fails.

DMARC Policies

• p=none: Monitor only (start here)
• p=quarantine: Send failures to spam
• p=reject: Block failures entirely

A Complete DMARC Record

v=DMARC1; p=quarantine; sp=quarantine; rua=mailto:[email protected]; pct=100

Implementation Roadmap

Week 1-2: Inventory

• List all services sending email as your domain
• Document current authentication status

Week 3-4: SPF Implementation

• Create comprehensive SPF record
• Include all legitimate senders
• Test with online validators

Week 5-6: DKIM Setup

• Generate key pairs
• Publish public keys in DNS
• Configure signing on all mail servers

Week 7-8: DMARC Deployment

• Start with p=none
• Monitor reports for issues
• Gradually move to p=quarantine, then p=reject

Common Mistakes to Avoid

1. Too many DNS lookups: SPF has a 10-lookup limit
2. Missing third-party senders: Don't forget marketing tools
3. Moving to reject too quickly: Monitor first!
4. Ignoring DMARC reports: They reveal authentication failures

CalimaticMail Makes It Easy

We handle email authentication automatically:

• Auto-configured SPF records
• DKIM signing enabled by default
• DMARC reporting dashboard
• One-click policy upgrades

Secure your email today