Deliverability

How to reduce your email bounce rate

Bounces are the clearest signal to mailbox providers that a sender does not look after its list. These steps keep yours low.

Updated October 1, 2026 · 1 min read

Hard vs. soft bounces

TypeCauseSMTP codeAction
HardMailbox or domain does not exist550 5.1.1, 5.1.2Remove at once
SoftMailbox full, server busy, greylisting421, 450, 452Retry; remove after 3–5 failures
BlockYour server or content was rejected550 5.7.xFix authentication or reputation

7 ways to reduce bounces

  1. Validate at sign-up. Stop typos and fake addresses at the source with a real-time check (API or the validator).
  2. Clean old lists before sending. Run them through the bulk email validator and remove undeliverable addresses.
  3. Use double opt-in for newsletters, so only confirmed addresses get on the list.
  4. Block disposable addresses that stop working after a few hours (disposable checker).
  5. Set up SPF, DKIM and DMARC so your mail is not rejected as unauthenticated. Check them with the SPF, DKIM and DMARC checkers.
  6. Remove hard bounces automatically and stop sending to soft bounces after repeated failures.
  7. Re-engage or sunset inactive contacts. Addresses that have not opened in 6–12 months are the next bounces.

Frequently asked questions

What is a good email bounce rate?

Below 2% is the commonly used benchmark, and well-kept lists stay under 1%. Many email service providers review or pause accounts with consistently higher rates.

What is the difference between a hard and a soft bounce?

A hard bounce is permanent: the address or domain does not exist (5xx error). A soft bounce is temporary: a full mailbox, a server that is down or a message that is too large (4xx error). Remove hard bounces immediately; remove soft bounces after several failures in a row.

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 docs

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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. Gmail and Yahoo sender requirementsWhat 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. 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. 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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