Software Development · A Cranfill Product

Mail Arbiter

A considered second opinion on any email you doubt. Phishing, an account you never opened, or simply legitimate. Examined on your own computer, not on ours.

In Beta Chrome Extension macOS 13 or later Gmail · Outlook on the web
The Verdict

One message, judged plainly.

Every signal shown
Phishing

An attempt to deceive.

Forged senders, look-alike domains, links that go somewhere other than they claim.

Unsolicited

An account you did not open.

Welcome and verification messages for sign-ups made in your name by someone else.

Legitimate

What it appears to be.

The sender is authenticated, the domain is established, and the content is consistent.

Where the evidence conflicts, Mail Arbiter says it is inconclusive rather than guess. Each verdict comes with the full breakdown of signals behind it.

Method

What it examines

Four Lines of Inquiry
01 Authentication Whether the message passed SPF, DKIM and DMARC, meaning whether the sending server was actually permitted to send for that domain.
02 Sender & Domain The age and registrar of the sender's domain and its return path, looked up from public records. Newly registered domains warrant caution.
03 Links & Content Where each link really leads, the brands the message invokes, and the familiar language of urgency and pretext.
04 CoherenceOptional · Off by default Whether the message is consistent with the sender's own public website. This check uses Claude with your own Anthropic key, and only runs when you tick the box for that message.
Two Parts

In the browser, and on the desk.

I · The Extension

Analyze with Mail Arbiter

A Chrome extension that adds one action to Gmail and to Outlook on the web. It reads a message only when you ask, and shows the verdict in a side panel next to the message.

Mail Arbiter's side panel showing a Phishing verdict with high confidence and a breakdown of eight signals, next to the analyzed email
II · The Companion App

A quiet presence in the menu bar

A macOS app that runs the analysis on your own computer, reachable only from that computer. Press Start to begin and Stop to end it. It stays stopped until you press Start again.

The Mail Arbiter companion app window, showing the service running, with buttons to add the extension to Chrome or Brave
Privacy

Your correspondence is read on your machine, and nowhere else.

Cranfill Enterprises operates no server that receives your email. The analysis runs on your computer, and the message is held in memory only as long as it takes to judge it.

  • Email content, to any Cranfill server Never
  • Analytics, telemetry, usage statistics Never
  • Domain names, for public registry lookups To look up domains
  • Short excerpts, to Anthropic, with your key Only if you tick the box
Read the Privacy Policy
Install · Beta

Two parts, both required.

Install the companion app on your Mac, then add the extension to Chrome. The app will offer to add it for you.

Questions or feedback: mailarbiter@cranfillenterprises.com

I · Download for macOS Companion app · v0.1.0 II · Add to Chrome Chrome Web Store