What is “policy rejection”?

You sent an email, it bounced, and the error message says something like "550 5.7.1 Message rejected due to policy" or "554 Policy violation." What does that actually mean?

A policy rejection is a hard block where the receiving mail server refused your message because it broke a rule that server has explicitly set. It's not a spam filter guessing your content is bad. It's the server saying "our rules say no" before it even looks at your subject line.

Those rules can cover a lot of ground:

• Authentication failures. The server requires SPF, DKIM, or DMARC to pass, and yours didn't.
• Sender reputation. Your IP or domain is on a blocklist or has a poor sending history.
• Allowlist-only setup. The recipient's server only accepts mail from pre-approved senders (common in corporate environments).
• TLS encryption required. The server demands an encrypted connection and your setup didn't negotiate one.
• Rate limits. You sent too much too fast and hit the server's volume threshold.
• Content type rules. Certain attachment types (like.exe files) are blocked outright by admin policy.

The key difference between a policy rejection and spam content rejection is this: spam filtering is probabilistic. It weighs signals and makes a judgment call. Policy rejection is binary. You either meet the rule or you don't. Content quality is irrelevant.

Common SMTP codes you'll see with policy rejections are 550 or 554, often paired with extended codes like 5.7.1 (not authorized by policy) or 5.7.0 (delivery not authorized). The full error message usually hints at which rule you've hit. Read it carefully before trying anything else.

To fix it, start with the most common cause first. Check that your SPF, DKIM, and DMARC records are correctly set up and passing. If authentication is clean, check whether your domain or sending IP is on a blocklist. If you're sending to a corporate domain and getting this on transactional mail, you may need to contact their IT team directly.

You can run a quick check on your domain's authentication with our free SPF Checker or Blocklist Checker to rule out the two most common causes. If the error message is cryptic and you're not sure what triggered it, feel free to bring it to our SOS Hotline and we'll take a look.