What are the key fields to look for in a bounce message?

Critical DSN fields for bounce processing:

Status:

Enhanced status code (5.1.1, 4.2.2, etc.). Primary classification signal. X.Y.Z format per RFC 3463.

Diagnostic-Code:

Full SMTP response from remote server. Contains detailed error message. May include provider-specific codes.

Final-Recipient:

The address that failed. May differ from original if forwarded. Essential for suppression.

Action:

"failed" = permanent. "delayed" = temporary, still trying. "delivered" = success (in positive DSNs).

Remote-MTA:

Server that generated the error. Helps identify provider. Useful for troubleshooting.

Arrival-Date:

When failure occurred. Useful for tracking and debugging.

These fields tell the complete story. Status for category, diagnostic for detail, recipient for action.