Deliverability

Gmail and Yahoo sender requirements

Since February 2024, Gmail and Yahoo enforce authentication and unsubscribe rules. Here is the checklist, and how to test your own email against it.

Updated October 1, 2026 · 2 min read

Requirements for everyone

Additional requirements for bulk senders

Checklist

RequirementHow to checkTypical fix
SPFSPF checkerAdd your email service’s include:
DKIM with your domainDKIM checkerEnable domain authentication at your email service
DMARC recordDMARC checkerv=DMARC1; p=none; rua=mailto:…
Reverse DNSSpam checkerPTR record via your hosting provider
One-click unsubscribeSpam checkerEnable List-Unsubscribe in your email tool
Low complaint rateGoogle Postmaster ToolsOnly send to people who opted in; clean your list

Frequently asked questions

Who counts as a bulk sender?

Google defines bulk senders as those sending close to 5,000 or more messages a day to personal Gmail accounts. Once you reach that, you stay a bulk sender. Yahoo applies similar rules without publishing an exact number.

What happens if I do not meet the requirements?

Messages are increasingly rejected or delivered to spam. Google returns errors that link to its sender guidelines.

How do I check my email against these requirements?

Send a message to the email spam checker. It shows SPF, DKIM, DMARC, reverse DNS, List-Unsubscribe and the SpamAssassin score in one report.

Email validation API

Validate emails in your app

emailvalidation.io checks syntax, MX records and the mailbox over SMTP, flags disposable, role and free addresses and returns a quality score, in one request.

/v1/info Email validation API Read the documentation

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GET https://api.emailvalidation.io/v1/info?email=support@emailvalidation.io

{
  "email": "support@emailvalidation.io",
  "domain": "emailvalidation.io",
  "format_valid": true,
  "mx_found": true,
  "smtp_check": true,
  "disposable": false,
  "role": true,
  "free": false,
  "score": 0.64,
  "state": "deliverable",
  "reason": "valid_mailbox"
}

Keep reading

Best email validation APIs in 2026Email verification APIs compared: emailvalidation.io, ZeroBounce, NeverBounce and Kickbox. Checks, free tiers and price per email at 5,000 to 100,000 verifications. Catch-all email addresses explainedWhat a catch-all (accept-all) domain is, why email verifiers mark these addresses as risky, how to detect catch-all domains and whether you should send to them. How to check if an email address existsHow email verification works: syntax, DNS and MX lookup, and the SMTP RCPT TO handshake that asks the mail server about a mailbox without sending a message. Plus its limits: catch-all, greylisting. How to reduce your email bounce rateWhat hard and soft bounces are, what bounce rate is acceptable, and seven ways to lower it: validation at sign-up, list cleaning, double opt-in, SPF, DKIM and DMARC. Validate email addresses in JavaScriptValidate emails in JavaScript: HTML5 input validation, a practical regex, typo hints, and checking that the mailbox exists with an API call from Node.js. Copy-paste code. Validate email addresses in PHPValidate emails in PHP with filter_var, check MX records with checkdnsrr, and verify the mailbox with an API call using cURL or Guzzle. Laravel validation rule included.

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