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InboxStackGPT · Free · Google Postmaster Tools

Ask Claude which of your domains Gmail is about to throttle.

InboxStackGPT reads your Google Postmaster Tools data across every domain you send from: spam rate, SPF, DKIM, DMARC, one-click unsubscribe. Ask in plain English and get the worst domains first, with the exact fix for each.

Works with Claude and ChatGPT. Read-only. Sign in with the Google account you use for Postmaster Tools.

Example
What’s the health of my domains?

5 domains checked over the last 7 days: 1 critical, 1 warning, 2 healthy, 1 without enough Gmail traffic to report.

  1. acme-mail.com — critical. Spam rate peaked at 0.45%, above Google’s 0.30% limit. DMARC policy is missing and one-click unsubscribe isn’t set up. Publish a record at _dmarc.acme-mail.com and add List-Unsubscribe-Post headers first.
  2. news.acme.com — warning. Spam rate reached 0.15%, above Google’s 0.10% target. Suppress recipients who haven’t opened in 90 days.

acme.com and billing.acme.com pass every check.

Set up in a minute

Add it to the assistant you already use.

  1. 1
    In Claude, open Settings → Connectors and choose Add custom connector.
  2. 2
    Name it InboxStackGPT and paste https://gpt.inboxstack.com/mcp.
  3. 3
    Click Connect, sign in with Google and allow read access to Postmaster Tools.
  4. 4
    Start a chat and ask: “What’s the health of my domains?”

What you can ask

Questions you’d otherwise answer by clicking through Postmaster, one domain at a time.

  • “What’s the health of my domains?”
  • “Which domains are over Google’s 0.3% spam limit this week?”
  • “Why is acme-mail.com non-compliant, and how do I fix it?”
  • “Show news.acme.com’s spam rate for the last 30 days.”
  • “Which of my domains are missing one-click unsubscribe?”
InboxStackGPT browser extension listing five domains, worst first, with spam rates
The Chrome and Firefox extension: every domain in one list, with an alert when one gets worse. Example data.

What it checks

Everything Google reports in Postmaster Tools v2.

Spam rate

Daily user-reported spam rate against Google’s 0.10% target and 0.30% limit.

SPF and DKIM

Whether Gmail sees every message authenticated.

DMARC alignment and policy

Whether your From domain lines up, and whether a DMARC record exists.

TLS encryption

Whether your mail arrives over an encrypted connection.

DNS records

Forward and reverse DNS for your sending IPs.

One-click unsubscribe

List-Unsubscribe-Post headers on marketing mail, and whether unsubscribes are honored.

Delivery errors

Rejects and temporary failures, by type.

Subdomains

Google’s compliance verdict for subdomains as well as the parent domain.

Your data

Read-only, and your Google tokens never leave InboxStack.

  • Read-only scopes. InboxStackGPT can list your Postmaster domains and read their traffic and compliance data. Nothing else.
  • Encrypted at rest. Google tokens are encrypted on InboxStack’s server. Claude, ChatGPT and the extension get their own short-lived InboxStackGPT tokens instead.
  • Only your domains. Every request is checked against the domains your own Google account can see.
  • Not for ads or model training. Postmaster data is used only to answer your questions. Read the privacy notice.

Questions

Is it really free?
Yes. There is no trial, no card and no domain limit. Connect as many Postmaster domains as your Google account can see.
What does InboxStackGPT need access to?
Read-only access to your Google Postmaster Tools domains and traffic data. It cannot send email, read your inbox, or change anything in Postmaster Tools. See the InboxStackGPT privacy notice for exactly what is stored.
My domain shows “no data”. Why?
Google only reports on domains that send a meaningful daily volume to Gmail users. Low-volume domains, and domains that are not yet verified in Postmaster Tools, come back empty. InboxStackGPT tells you that instead of guessing.
Does Claude or ChatGPT see my Google password or tokens?
No. You sign in with Google on InboxStack’s own page. Your Google tokens are encrypted and stay on InboxStack’s server; Claude and ChatGPT only receive the answers to the questions you ask.
How do I disconnect?
Remove the connector in Claude or ChatGPT, and revoke InboxStackGPT at myaccount.google.com/permissions. To delete your InboxStackGPT data entirely, email help@inboxstack.com.
Is there a browser extension?
Yes, for Chrome and Firefox. It shows every domain in one list and alerts you when a domain gets worse. It is on its way to the Chrome Web Store and Firefox Add-ons.

A client asked what is going on?

Answer with a report, not a guess.

InboxStackGPT shows what Google sees. Run a free audit to check the headers and DNS behind a single message.

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