What are “policy” or “spam-related” bounces?

Policy bounces and spam-related bounces look like standard delivery failures, but the reason isn't that the address doesn't exist. It's that the receiving system has decided not to accept your message, for one reason or another.

These typically come back as 550 or 554 SMTP response codes with message text that references spam, policy violations, or blocklists. Common examples:

• "550 5.7.1 Message rejected because of policy" (generic policy block)
• "550 5.7.0 Our system has detected that this message is likely unsolicited mail"
• "554 5.7.1 Service unavailable; Client host [IP] blocked using [blocklist name]"
• "550 5.7.1 Your message was detected as spam"

The distinction from hard bounces matters. A hard bounce like "user unknown" is about the address. A policy bounce is about you, specifically your sending domain, your IP address, or the content of your message. Removing the bounced address won't fix the underlying problem.

The most common causes:

• Domain or IP reputation: Your sending domain or IP is on a blocklist that the receiving server checks. This affects delivery to all addresses at that provider, not just the one that bounced.
• Authentication failures: SPF, DKIM, or DMARC not set up correctly, which causes some providers to reject or filter your messages as a policy matter.
• Content triggers: Specific words, link patterns, or formatting in your email that match known spam signatures.
• Recipient history: The individual recipient has previously marked emails from your domain as spam, and the provider is honoring that preference at the server level.

If you're seeing a pattern of policy bounces, especially to the same domain, check whether you're blocklisted at that provider. Our free blocklist checker can confirm that in about 30 seconds. If the issue is authentication, fix your DNS records before retrying.