How does Gmail’s bulk sender rejection appear in logs?

Gmail bulk sender rejections have distinctive patterns:

Common rejection formats:

"550-5.7.1 Our system has detected that this message is likely spam." "550-5.7.26 This message does not have authentication information." "421-4.7.0 Connection rate limit exceeded." References to support.google.com documentation.

2024 bulk sender requirements:

Senders of 5,000+ messages per day to Gmail must comply with specific requirements. Authentication (SPF, DKIM, DMARC) mandatory. Easy unsubscribe required. Complaint rates below threshold.

Rejection indicators:

Messages reference "bulk sender" policies. Links to Gmail postmaster documentation. Specific enhanced codes (5.7.26 for auth).

Resolution:

Review Gmail postmaster guidelines. Ensure full authentication compliance. Implement one-click unsubscribe. Monitor via Google Postmaster Tools.

Gmail publishes clear requirements. Bulk sender rejections usually cite exactly which rule was broken.