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Email error Spam rejection: Message flagged as spam

The receiving server judged the message to be spam and refused it. The reason is in the content, the sender reputation or the sending pattern, not in the address itself.

Sender or policy problem

What it means

The receiving server judged the message to be spam and refused it. The reason is in the content, the sender reputation or the sending pattern, not in the address itself.

Common causes

  • Spammy wording, too many links or a large image with little text.
  • A poor sender reputation or a blocklisted IP.
  • Mail sent to many invalid addresses and spam traps.
  • Missing authentication.

How to fix it

  1. Rewrite the message in plain, honest language and keep links few.
  2. Authenticate the domain with SPF, DKIM and DMARC.
  3. Clean the list so you stop hitting dead addresses and traps.
  4. Send to people who asked for the mail and make unsubscribing easy.

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

Can a verified list still be flagged?

Yes. Verification removes bad addresses. Content and reputation still matter.

How do I test the message?

Send it to a few mailboxes you control and check where it lands.

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