What is the difference between 550 5.7.1 and 554 5.7.1?

They are functionally identical. 550 usually means 'mailbox unavailable due to policy', while 554 means 'transaction failed due to policy'. Both indicate a spam or policy block.

How do I fix a Spamhaus listing?

Visit the Spamhaus blocklist removal center, look up your IP, and follow their instructions. Ensure you have fixed the root cause (e.g., compromised server) before requesting delisting.

← Error library

554 5.7.1 Message rejected / Spam block

permanent Policy

Meaning

The receiving server rejected your message due to a strict security policy, often because it was classified as spam or your sending IP is blacklisted.

Common causes

Your sending IP or domain is on a major blacklist (e.g., Spamhaus, Sorbs).
The recipient's server uses strict anti-spam filters that flagged your content.
Your email lacks proper authentication (SPF, DKIM, DMARC).

How to fix

Check your sending IP and domain against blacklists and request delisting.
Verify your SPF, DKIM, and DMARC records are correctly configured.
Review your email content to ensure it does not look like spam.

Provider notes

Amazon SES. Often returned by ISPs when the sender reputation is too low.

Example bounce

554 5.7.1 Service unavailable; Client host [192.0.2.1] blocked using zen.spamhaus.org.

FAQ

What is the difference between 550 5.7.1 and 554 5.7.1?: They are functionally identical. 550 usually means 'mailbox unavailable due to policy', while 554 means 'transaction failed due to policy'. Both indicate a spam or policy block.
How do I fix a Spamhaus listing?: Visit the Spamhaus blocklist removal center, look up your IP, and follow their instructions. Ensure you have fixed the root cause (e.g., compromised server) before requesting delisting.