How do “delivery errors” correlate with reputation scores?

Delivery errors in Gmail Postmaster Tools indicate messages that failed during the SMTP transaction. While some errors are technical (DNS issues, server timeouts), many correlate with reputation problems.

High error rates often signal that Gmail is rejecting or deferring your mail due to reputation concerns. The errors may include rate limiting, policy blocks, or authentication failures.

Correlating delivery errors with reputation graphs helps diagnose issues. If errors spike while reputation drops, the errors are likely reputation-driven. If errors spike with stable reputation, look for technical causes.

Persistent delivery errors without resolution compound reputation damage. Each failed delivery attempt that Gmail tracks adds to the pattern of problematic sending.

Delivery errors are like ships being turned away at the harbor entrance. Sometimes the channel is blocked. Sometimes the harbor closed early. But often, it means authorities do not trust your vessel enough to let it dock.