How to investigate SendGrid evidence
A SendGrid configuration can affect authentication through several DNS and message-level identities. Mailybox helps reveal which evidence belongs to the provider, which belongs to the customer domain and which still needs verification from a real message.
Signals worth checking
- SPF include references
- DKIM selector delegation
- Return-Path identity
- Bounce diagnostics
- Coexisting third-party senders
Diagnostic path
- Use a real header to inspect the signing domain and return path.
- Do not remove an SPF authorization until its dependency is understood.
- Treat a provider fingerprint as evidence of configuration, not proof of current sending activity.
- Retest DMARC after domain-authentication changes.
Questions this hub can answer
- Is SendGrid publicly authorized for this domain?
- Which DKIM identity signed this message?
- Why can DMARC fail when a provider says authentication passed?
- What else shares the domain’s SPF policy?