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Prompt

dkim spf dmarc email api

Technology / Developer Tools1 observationLast seen Oct 6, 2026

Latest observation

Oct 6, 2026OpenAI APIWeb search: off

If you’re looking to send email through an API and want it to land reliably in inboxes, you should set up:

  • SPF: authorizes which servers can send for your domain
  • DKIM: cryptographically signs outgoing mail
  • DMARC: tells receivers how to handle mail that fails SPF/DKIM and gives you reports

What each one does

  • SPF: “These IPs/services are allowed to send for my domain.”
  • DKIM: “This message really came from me and wasn’t altered.”
  • DMARC: “Only accept mail if it passes SPF or DKIM and aligns with my domain.”

Typical setup for an email API

If you use a provider like SendGrid, Mailgun, Amazon SES, Postmark, Brevo, etc.:

  1. Verify your sending domain in the provider
  2. Add SPF record they give you to DNS
  3. Add DKIM CNAME/TXT records they give you to DNS
  4. Add DMARC record to your DNS
  5. Test with a few emails and check headers/authentication results

Example DNS records

These are generic examples; your provider will give exact values.

SPF

v=spf1 include:spf.protection.example.com include:sendgrid.net ~all

DKIM Usually provided as one or more CNAME records, for example:

s1._domainkey.example.com CNAME s1.domainkey.provider.com
s2._domainkey.example.com CNAME s2.domainkey.provider.com

DMARC

v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com; adkim=s; aspf=s

Best practice

  • Start DMARC with p=none to monitor
  • Move to quarantine
  • Then move to reject once everything is aligned
  • Make sure your From domain matches the authenticated domain as closely as possible

Common reasons email fails

  • SPF record has too many lookups
  • Multiple SPF records exist
  • DKIM not enabled or DNS record missing
  • DMARC alignment mismatch
  • Sending from a different domain than the one authenticated

If you mean “how do I do this via an API?”

Most email APIs have a domain authentication section where you:

  • create a domain
  • get DNS records back
  • add them in your DNS provider
  • verify the domain
  • then send mail via the API

If you want, I can give you:

  1. a step-by-step setup for a specific provider like SendGrid/Mailgun/SES, or
  2. the exact SPF/DKIM/DMARC records for your domain/provider.

Brands

TwilioMailgunAmazon SesPostmarkBrevo

Observation history

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