Email validation guides
Guides on validating email addresses in JavaScript, Python and PHP, checking if an email exists, catch-all domains, bounce rates and choosing an email verification API.
Tutorial · Python
Validate email addresses in Python
Validate emails in Python: syntax checks with email-validator, MX lookups with dnspython, and verifying the mailbox exists with an API call. Includes bulk validation of a CSV.
Tutorial · PHP & Laravel
Validate email addresses in PHP
Validate 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.
Tutorial · JavaScript & Node.js
Validate email addresses in JavaScript
Validate 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.
Deliverability
How to reduce your email bounce rate
What 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.
Explainer
How to check if an email address exists
How 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.
Deliverability
Gmail and Yahoo sender requirements
What Gmail and Yahoo require from email senders: SPF or DKIM for everyone; SPF, DKIM, DMARC, one-click unsubscribe and a spam rate below 0.3% for bulk senders. Checklist with fixes.
Explainer
Catch-all email addresses explained
What 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.
Comparison
Best email validation APIs in 2026
Email verification APIs compared: emailvalidation.io, ZeroBounce, NeverBounce and Kickbox. Checks, free tiers and price per email at 5,000 to 100,000 verifications.
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.
Read the docs100 free validations every month. No credit card required.
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"
}