Gmail message blocked

Exact response pattern550 5.7.1 Our system has detected that this message is likely unsolicited mail

PermanentGmailReputation

What it means

Gmail classified the message or sender as likely unsolicited.

Likely causes

Low reputation.
Complaint history.
Poor list consent.
Content and link reputation.

Recommended response

Stop the affected campaign.
Review consent and engagement.
Inspect authentication and Postmaster data.
Do not resend unchanged to the same recipients.

Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.

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