How do you confirm reputation is the root cause?

Confirming reputation as the root cause requires checking multiple sources:

Postmaster Tools at Gmail, Microsoft SNDS, and Yahoo show reputation scores and trends. If scores dropped, reputation is likely the cause.

Blocklist lookups via MXToolbox or MultiRBL reveal if your IP or domain appears on any major lists.

Bounce message analysis shows whether rejections cite reputation, policy, or blocklist reasons rather than technical failures.

Authentication verification confirms SPF, DKIM, and DMARC are passing. If authentication broke, that might be the root cause instead.

Cross-provider comparison helps. If problems appear only at one provider, the cause may be specific to their systems.

Diagnosis requires examining all the instruments. A captain who only checks one gauge may miss the actual problem while treating a symptom.