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Domain Authentication · chunkydotdev | DecimalAI

devopsby chunkydotdev

Domain Authentication

chunkydotdev/domain-authentication

Source chunkydotdev/email-skills ↗License MIT

Set up SPF, DKIM, and DMARC email authentication.

SkillScore86Maintained

Automatic

DevOps & SRE pack

Last verified 8/6/2026

What it changes

Passed 19 of 22 test cases with the skill, and 15 of 22 without it.

Without skill68%

With skill86%

Checks it passed that the model alone missed

The final SPF record ends with -all rather than ~all.
The DMARC monitoring record includes sp=reject explicitly.
The response states that Microsoft Outlook does not support BIMI logos.

and 1 more in the full report

4 fixed15 passed either way3 still failing0 broke

Pass-rate lift: +18 pp
Tokens: +178%
Agent turns: 0%
Response time: -28%

Model gemini-3.6-flashMeasured 8/6/2026v119 of 22 cases passed with skill

Tokens, turns and time describe resource use, not a dollar price.

Use this skill

Save it into your project's skills folder. Claude Code picks it up in its next session.

curl -fsSL --create-dirs -o .claude/skills/chunkydotdev-domain-authentication/SKILL.md https://app.decimal.ai/s/chunkydotdev-domain-authentication/SKILL.md

Want it pinned and updatable? pip install "decimalai>=0.15", then decimalai skills add chunkydotdev-domain-authentication, and start Claude Code with claude --plugin-dir "$(git rev-parse --show-toplevel)/.agents"

1 · One-time — install the CLI (docs ↗)

pip install "decimalai>=0.15"

2 · Get the skill — writes .agents/skills/chunkydotdev-domain-authentication/ and pins it in .decimal/skills.lock

decimalai skills add chunkydotdev-domain-authentication

No CLI? Get the same file — curl · raw file

curl -fsSL --create-dirs -o .claude/skills/chunkydotdev-domain-authentication/SKILL.md https://app.decimal.ai/s/chunkydotdev-domain-authentication/SKILL.md

Raw file: /s/chunkydotdev-domain-authentication/SKILL.md ↗ · machine-readable summary at /s/chunkydotdev-domain-authentication.json ↗

Safety checks: 3 of 3 passed

Code scan CleanIntent PassedContent Clean

See it in action

One of 4 test cases the skill fixed. Same model, same prompt, with and without the skill.

1 of 4

Prompt

We have two separate TXT records on our root domain for SPF because team A added "v=spf1 include:_spf.google.com ~all" and team B added "v=spf1 include:sendgrid.net ~all". We've verified all sending hosts and want a permanent production-ready setup. Provide the consolidated DNS record.

What was checked, without and with the skill
Checked	Without skill	With skill
The output combines all authorized mechanisms into a single v=spf1 record.	Passed	Passed
The final SPF record ends with -all rather than ~all.	Missed	Passed

case-02 · gemini-3.6-flash · 8/6/2026 · answers are capped and redacted

What's inside

The instructions your model reads when the skill loads.

SKILL.md356 linessingle file

Domain Authentication

Set up SPF, DKIM, and DMARC so your emails actually reach the inbox.

When to use this skill

Setting up email sending for a new domain
Emails are landing in spam or being rejected
Adding a new email provider or SaaS tool that sends on your behalf
Preparing for Google/Yahoo/Microsoft bulk sender requirements
Auditing an existing domain's authentication setup
Locking down a domain that doesn't send email

Related skills

email-warmup - after authentication is in place, ramp sending volume gradually
provider-setup - choose and configure an email provider
bounce-handling - handle delivery failures and protect your reputation
email-compliance - legal requirements (CAN-SPAM, GDPR, unsubscribe)

The authentication stack

Three protocols work together. All three are required - not optional - for any domain sending email in 2025+.

Protocol	What it does	DNS record type
SPF	Declares which servers can send email for your domain	TXT on domain root
DKIM	Cryptographically signs each message to prove it wasn't tampered with	TXT or CNAME on selector subdomain
DMARC	Tells receivers what to do when SPF/DKIM fail, and sends you reports	TXT on `_dmarc` subdomain

A message passes DMARC if either SPF or DKIM passes and aligns with the From domain. Both should pass, but only one is required.

SPF (Sender Policy Framework)

SPF declares which IP addresses and services are authorized to send email for your domain.

Track record

Benchmark

19 / 22

test cases passed, vs 15 / 22 without

Adoption

Users: 0
Times used: 0

Safety and source details

SkillSafety

✓ 3 of 3 passed

Code scan15 of 15 checks clean

0 critical · 0 warning · 0 info — scanner v4 — 8/2/2026

View 15 scanner checks

live_secretremote_code_executionreverse_shelldata_exfiltrationssrf_metadataagent_snoopinganti_refusaldestructive_commandsobfuscated_unicodeunicode_homoglyphopaque_blobsuspicious_urltool_overreachtrigger_abuseprompt_injection_phrasing

IntentSafe

LLM judge · does the skill do what it claims

ContentClean

LLM judge · policy & harmful-content review

Source

Imported

chunkydotdev / email-skills

skills/setup/domain-authentication/SKILL.md

View on GitHub ↗

License MITImported 8/2/2026Version v1

Other skills for the same job

Published skills whose descriptions closely match this one, with their headline benchmark lift.

rampstackco/email-deliverabilityMake sure email actually reaches inboxes. Use this skill when setting up email authentication (SPF, DKIM, DMARC), diagnosing emails landing in spam, planning a domain reputation strategy, monitoring sender reputation, or hardening against email spoofing. Triggers on email deliverability, SPF, DKIM, DMARC, spam folder, sender reputation, mailbox provider, soft bounces, bounce rate, BIMI, MTA-STS, deliverability audit. Also triggers when a marketing or transactional email isn't reaching users.Close match+13 pp pass-rate lift

More skills from the same source and nearby in the registry, with their headline benchmark lift.