What logs or headers should be collected during diagnosis?

Essential data collection for diagnosis:

Email headers:

Authentication-Results (SPF, DKIM, DMARC)

Received headers (routing path)

X-headers from ESP or filters

SMTP logs:

Connection status and errors

Response codes from receivers

Timing and throughput data

Bounce logs:

Error codes and messages

Receiving server responses

Timestamp correlation

Sending records:

Campaign details (time, volume, segment)

List source information

Content that was sent

External data:

Postmaster tool screenshots

Blocklist check results

Third-party reputation scores

Comprehensive data enables accurate diagnosis.

Ship logs, cargo manifests, port records, and inspection reports all tell part of the story.