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Email error 421 4.4.1: Connection timed out

Your server could not reach the recipient server in time. Nothing was refused; the connection simply failed or was too slow.

Temporary failure (soft bounce)

What it means

Your server could not reach the recipient server in time. Nothing was refused; the connection simply failed or was too slow.

Common causes

  • The recipient server is down or overloaded.
  • A firewall or network problem between the servers.
  • The recipient domain has a wrong or dead MX host.
  • Your own server cannot make outbound connections on the mail port.

How to fix it

  1. Let the system retry; most timeouts clear on their own.
  2. Check that your server can reach other mail servers, to rule out a local problem.
  3. Run an MX lookup on the recipient domain and see whether the host answers.
  4. If it never works for a domain, treat its addresses as undeliverable.

How to prevent it

Most bounces come from addresses that were never checked. Verify each address before you send: syntax, domain, mailbox and risk are checked without sending a message. Test a single address with the free email checker or upload a whole list for bulk verification.

Verify an email address free · Clean a whole list · MX lookup · SPF, DKIM and DMARC checker

Frequently asked questions

Is the address bad?

Not necessarily. It may be a network problem.

How many retries are normal?

Mail systems usually retry for several days before giving up.

Other error codes

550 5.1.1User unknown (mailbox does not exist) 550 5.7.1Message rejected by policy (blocked) 550 5.7.26Sender not authenticated (SPF/DKIM/DMARC) 550 5.4.1Recipient address rejected: access denied 552 5.2.2Mailbox full (over quota) 553 5.1.3Invalid address syntax

All email error codes