SPF, DKIM, and DMARC form the three pillars of email authentication. Together they prevent domain spoofing, validate message integrity, and define policies for handling unauthenticated mail. Proper im
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Before installing skills in Cursor, ensure your development environment meets these requirements:
node --versionimplementing-dmarc-dkim-spf-email-securityExecute the skills CLI command in your project's root directory to begin installation:
Fetches implementing-dmarc-dkim-spf-email-security from mukul975/Anthropic-Cybersecurity-Skills and configures it for Cursor.
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Confirm successful installation by checking the skill directory location:
Restart Cursor to activate implementing-dmarc-dkim-spf-email-security. Access via /implementing-dmarc-dkim-spf-email-security in your agent's command palette.
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| name | implementing-dmarc-dkim-spf-email-security |
| description | SPF, DKIM, and DMARC form the three pillars of email authentication. Together they prevent domain spoofing, validate message integrity, and define policies for handling unauthenticated mail. Proper im |
| domain | cybersecurity |
| subdomain | phishing-defense |
| tags | - phishing - email-security - social-engineering - dmarc - awareness - dkim - spf - dns |
| version | '1.0' |
| author | mahipal |
| license | Apache-2.0 |
| nist_csf | - PR.AT-01 - DE.CM-09 - RS.CO-02 - DE.AE-02 |
SPF, DKIM, and DMARC form the three pillars of email authentication. Together they prevent domain spoofing, validate message integrity, and define policies for handling unauthenticated mail. Proper implementation drastically reduces phishing attacks that impersonate your organization's domain.
Publishes a DNS TXT record listing authorized IP addresses and mail servers that can send email on behalf of your domain. Receiving servers check the envelope sender's IP against this list.
Adds a cryptographic signature to outgoing emails using a private key. The corresponding public key is published in DNS. Receivers verify the signature to ensure the message was not altered in transit.
Builds on SPF and DKIM by specifying a policy (none/quarantine/reject) for messages that fail authentication, and provides a reporting mechanism to monitor spoofing attempts.
# Check existing SPF record
dig TXT example.com | grep spf
# Check existing DKIM selector
dig TXT selector1._domainkey.example.com
# Check existing DMARC record
dig TXT _dmarc.example.com
# DNS TXT record for example.com
v=spf1 ip4:203.0.113.0/24 include:_spf.google.com include:spf.protection.outlook.com -all
Key SPF mechanisms:
ip4: / ip6: - Authorize specific IP rangesinclude: - Include another domain's SPF recorda - Authorize domain's A record IPsmx - Authorize domain's MX record IPs-all - Hard fail all others (recommended)~all - Soft fail (monitoring phase)# Generate DKIM key pair (2048-bit RSA)
openssl genrsa -out dkim_private.pem 2048
openssl rsa -in dkim_private.pem -pubout -out dkim_public.pem
# Format public key for DNS (remove headers, join lines)
grep -v "PUBLIC KEY" dkim_public.pem | tr -d '\n'
DNS TXT record at selector1._domainkey.example.com:
v=DKIM1; k=rsa; p=MIIBIjANBgkqhki...
# DNS TXT record at _dmarc.example.com
# Phase 1 (Monitor):
v=DMARC1; p=none; rua=mailto:[email protected]; ruf=mailto:[email protected]; pct=100
# Phase 2 (Quarantine):
v=DMARC1; p=quarantine; rua=mailto:[email protected]; pct=25
# Phase 3 (Reject):
v=DMARC1; p=reject; rua=mailto:[email protected]; pct=100
Use the scripts/process.py to parse DMARC aggregate XML reports and identify authentication failures, unauthorized senders, and spoofing attempts.
Prerequisites
Time Estimate
15-45 minutes depending on use case complexity
Steps
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Use when skill capabilities match your task, clear ROI on time saved, and you can validate outputs. Best for repetitive tasks, learning, and quality improvement.
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Avoid when task requires deep expertise you can't validate, involves sensitive decisions, or when learning process is more valuable than speed of completion.
mukul975/Anthropic-Cybersecurity-Skills
mukul975/Anthropic-Cybersecurity-Skills
mukul975/Anthropic-Cybersecurity-Skills
mukul975/Anthropic-Cybersecurity-Skills
mukul975/Anthropic-Cybersecurity-Skills
mukul975/Anthropic-Cybersecurity-Skills
implementing-dmarc-dkim-spf-email-security has been reliable in day-to-day use. Documentation quality is above average for community skills.
I recommend implementing-dmarc-dkim-spf-email-security for anyone iterating fast on agent tooling; clear intent and a small, reviewable surface area.
Keeps context tight: implementing-dmarc-dkim-spf-email-security is the kind of skill you can hand to a new teammate without a long onboarding doc.
Useful defaults in implementing-dmarc-dkim-spf-email-security — fewer surprises than typical one-off scripts, and it plays nicely with `npx skills` flows.
Keeps context tight: implementing-dmarc-dkim-spf-email-security is the kind of skill you can hand to a new teammate without a long onboarding doc.
Useful defaults in implementing-dmarc-dkim-spf-email-security — fewer surprises than typical one-off scripts, and it plays nicely with `npx skills` flows.
implementing-dmarc-dkim-spf-email-security has been reliable in day-to-day use. Documentation quality is above average for community skills.
Keeps context tight: implementing-dmarc-dkim-spf-email-security is the kind of skill you can hand to a new teammate without a long onboarding doc.
I recommend implementing-dmarc-dkim-spf-email-security for anyone iterating fast on agent tooling; clear intent and a small, reviewable surface area.
We added implementing-dmarc-dkim-spf-email-security from the explainx registry; install was straightforward and the SKILL.md answered most questions upfront.
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