Setting up the Gmail add-on

The add-on answers one question where it is asked: can this email be trusted? With a message open, Guard.ch verifies the sender's SPF, DKIM and DMARC against live DNS, weighs the sender's reputation, reads the content the way a sceptical analyst would, and settles on one plain answer: Looks safe, Be careful, High risk, or an honest Couldn't verify.

Nothing else about your inbox changes. The add-on sits in Gmail's right side panel until you call it. This guide covers what it shows, how sign-in works, what the analysis covers, and what each notice on the card means.

What it adds to Gmail

• The verdict, without being asked. With a message open, choose the Guard.ch icon in the right side panel and the whole-email analysis starts by itself. The card shows the posture, a headline, key facts, the evidence with its web sources, and what to do next. Reopen the same email and the stored verdict is back instantly; it is kept for six hours per message.
• Every link, ready to go. Below the verdict, the card lists the links found in the message (the first 15) and opens each one as its own investigation in a disposable cloud browser. A link whose visible text points at a different domain than its real target carries a warning label; that is the classic phishing shape, worth opening first.
• A paste box. At the bottom of the card, any URL from anywhere can be pasted and launched the same way, whether the scanner found it or not.

Install it

The add-on is a free install from the Google Workspace Marketplace and works with personal Gmail accounts and Google Workspace accounts alike:

1. In Gmail, click the + at the bottom of the right side panel (Get add-ons), or open the Google Workspace Marketplace directly.
2. Search for Guard.ch and open the listing.
3. Click Install and allow the requested access. The list is deliberately short: the add-on may read the message you are currently looking at when you use it, and nothing beyond that.
4. Back in Gmail, open any message and choose the Guard.ch icon in the right side panel. The analysis starts on its own.

Rolling it out to a whole organisation? A Google Workspace administrator can install the add-on centrally from the same Marketplace listing (the admin install), and it appears in everyone's side panel with no per-user step.

How sign-in works

There is no sign-in screen. The add-on runs under your Google identity, so it proves who you are to Guard.ch with a short-lived Google token, and Guard.ch signs you in on the spot; the first use creates a verified account for your Gmail address by itself. Link investigations carry the same proof, so the browser tab they open lands already signed in.

The add-on never sees or stores a password. It keeps only its own Guard.ch session, and uninstalling the add-on ends the arrangement completely.

What the analysis checks

The card hands Guard.ch a minimal copy of the open message: sender, recipients, subject, date and body. The server parses it, verifies SPF, DKIM and DMARC against live DNS, weighs the sender's reputation, and has the AI agent read the content. Everything returns in one response: the posture, a headline, key facts, the evidence with its web sources, and the advice.

The verdict is kept for six hours per message, so reopening an email never spends another run. A message over 25 MB is declined with a plain notice; its links below still work as the way in.

Opening links as investigations

Each listed link, and anything you paste, opens the Guard.ch launcher in a new browser tab: the page loads in a disposable browser in our cloud, streamed live with every request, cookie and redirect on the record, and your Gmail never touches the target. The card caps the list at the first 15 links it finds; the paste box covers anything beyond that.

What it can and cannot read

The add-on holds the narrowest Gmail permission there is: read-only access to the single message you have open, granted at the moment you use it. It cannot browse your mailbox, cannot send mail, and cannot see any other message.

What travels to Guard.ch is the reconstructed copy of that one message, for that one analysis. The add-on follows your Gmail language (English and German are built in) and stores nothing beyond its own session.

Works with

Gmail, personal and Google Workspace accounts

Install

Google Workspace Marketplace, free

Permissions

Read-only access to the currently open message, only when you use it

Sign-in

Automatic, via your Google identity; no password

Analysis

SPF, DKIM and DMARC verified live, sender reputation, AI verdict; kept six hours per message

Languages

English and German, following your Gmail language

Troubleshooting

Every notice the card can show has a short answer:

“Couldn't sign in to Guard.ch. Please try again.” The silent exchange with Google did not complete, usually a hiccup. Run the analysis again; if it keeps failing, remove the add-on and install it fresh so the consent is granted anew.

“Connecting an app or extension to Guard.ch requires a Guard.ch plan.” Your account is signed in but carries no active plan. Open the dashboard from the card, start the trial or pick a plan, and run the analysis again. On a team, ask your workspace manager for a seat.

“This email is too large to analyze in full.” The message is over the 25 MB limit, which is permanent for this email; the links listed below it still open as investigations.

“Couldn't analyze this email right now.” A transient failure or a rate limit. The retry button runs the same analysis again; a minute later is usually enough.

The Guard.ch icon is missing from the side panel. The side panel itself may be hidden: the small arrow in Gmail's bottom-right corner brings it back. In a Google Workspace organisation an administrator may also restrict Marketplace installs; the admin install covers everyone at once.

The verdict looks out of date. Verdicts are kept per message for six hours, so a reopened email shows the same read without spending a run. After that window the next open runs fresh on its own.

Other entry points

However a link reaches Guard.ch, it lands in the same capture and the same report. Pair the add-on with the browser extension for everything outside the inbox, or see what an investigation actually captures on the product page.