What is “550 5.7.1 – Message rejected as spam”?

550 5.7.1 is a common spam rejection code:

Breaking it down:

550: Permanent failure, do not retry. 5.7.1: Enhanced code meaning "delivery not authorized, message refused." 7: Security/policy related. 1: Not authorized.

Common causes:

Content triggered spam filters. Poor sender reputation. Blocklist match. Authentication failure. Policy violation.

What to do:

Read the full error message for specifics. Check authentication (SPF, DKIM, DMARC). Review content for spam triggers. Check IP and domain reputation. Query blocklists.

Important note:

This is about the message or sender, not the recipient. Suppressing the address will not help. Fix the underlying cause.

5.7.1 is the spam verdict. Your message was judged and found wanting.