Free diagnostic

Email header analyzer with automatic PII redaction.

Paste up to 64 KB of message headers to inspect required fields, dates, Message-ID, reply-path consistency, unsubscribe support, MIME, and common risk signals.

Analyze headersRun a full test

Inspect structure without retaining message data

The analyzer keeps only the header block in memory for the request, discards any pasted body, and redacts addresses, Message-IDs, and IP addresses before returning evidence.

  • Check Date, From, To, Subject, Message-ID, Received, MIME, and mailer fields.
  • Inspect List-Unsubscribe and RFC 8058 one-click publication.
  • Use the full deliverability test for DKIM verification, DNS, content, and links.

Treat header findings as diagnostic evidence

A clean header block cannot guarantee inbox placement. Sender reputation, authentication alignment, recipient history, content, links, and provider behavior remain separate inputs.

Live diagnostic

Check current evidence

This anonymous tool is rate limited and does not retain submitted input. It reports observable evidence without promising delivery, authentication alignment, or inbox placement.

No SMTP mailbox probing, account lookup, or tenant data is used.

Enter an input to see current evidence, limitations, official references, and the relevant next step.

Related

List-Unsubscribe guide

Implement one-click handling correctly.

Plain text vs HTML

Understand MIME alternatives.

Deliverability tester

Analyze the complete sent message.

Reading The Willitinbox Report guide

Read the supporting guide for practical context around email deliverability testing.

Sample report example

Inspect the evidence format customers use to prioritize authentication, DNS, content, and placement fixes.

Deliverability testing docs

See how test inboxes turn authentication, DNS, headers, content, and link evidence into a launch-ready report.

API docs

Use the REST API reference when validation, bulk jobs, webhooks, reports, or usage need to run from your own systems.

Pricing

Compare validation volume, monitoring, API access, reporting, and workspace limits by plan.

FAQ