Permanent (5xx)
550 5.7.1
Message rejected as spam or policy violation
The receiving server's content or reputation filter rejected the message outright.
Common causes
- Sending domain/IP has poor reputation.
- Message content tripped a spam filter (spammy phrasing, broken HTML, no unsubscribe on bulk mail).
- Missing or failing SPF/DKIM/DMARC.
What to do
- →Confirm SPF, DKIM, and DMARC all pass for the sending domain.
- →Check the sending IP/domain isn't listed on a public blocklist (Spamhaus, Barracuda, etc).
- →Review message content for spam-trigger patterns if this is happening broadly, not to one recipient.