Validate Every Sender Domain in Your Inbox with Trusted Sender Score

Phishing is one of the most reported cybercrimes across Australia, with the Australian Cyber Security Centre regularly warning about criminals impersonating AusPost, myGov and the ATO through lookalike domains. For anyone managing a busy inbox in Sydney, Melbourne or a regional town, telling a genuine message from a fake one is rarely as simple as reading the sender name. The underlying sender domain, the part that follows the @ symbol, is often the only reliable clue, and Trusted Sender Score helps you check it in seconds.

Trusted Sender Score is a free cybersecurity platform that analyses the reputation, authentication and configuration of any sender domain. It runs checks against DNS records, DKIM signatures, DMARC policies and known spoofing indicators, then returns a clear trust verdict. The tool is built by Zulu Labs Inc. and is freely available at trusted sender score, so you can start verifying domains immediately without creating an account.

Why the sender domain matters

Every email is technically sent from a domain, and that domain can be checked before you open any attachment. In Australia, the Notifiable Data Breaches scheme under the Privacy Act 1988 has made organisations more accountable, yet attackers still slip through by registering addresses that mimic trusted brands. A message claiming to come from "commbank-update.com" instead of "commbank.com.au" is a classic example the eye easily misses.

Treating the sender domain as a verifiable object rather than a label shifts you from guessing to confirming. That mindset alone cuts a large slice of phishing risk, especially for small businesses in Brisbane and Perth without a dedicated security team.

How to run your first check

The main checker works for any individual address. You paste a sender address into the search field and the platform returns a score, the authentication status and any red flags. For a walk-through, follow the how to use guide, which explains each control and what the colour-coded results mean.

If the domain returns a low score, the platform will tell you whether DKIM is missing, whether DMARC is set to a permissive policy, or whether the domain has been flagged in threat feeds. That detail is useful when triaging a suspicious ATO-style message before reporting it to Scamwatch.

Reading the verdict

A high score means valid authentication, a long history and no known abuse patterns. A medium score usually signals records are present but configured loosely, which is common among smaller Australian businesses running mail on NBN connections and skipping the policy step. A low score should always be treated as a warning, regardless of how convincing the content appears.

When the result is failing, do not reply and do not open any PDF or ZIP attachment. Instead, hover over links to compare them against the verified domain, then forward the full headers to your IT contact or to the ACSC's ReportCyber service. Keeping a short log of these checks helps you spot repeat offenders targeting your address.

Bulk verification for shared mailboxes

Anyone running a shared inbox for a Sydney retailer, a Melbourne legal clinic or a Perth mining supplier will quickly find that checking domains one at a time is impractical. The bulk domain checker accepts a list of addresses and produces a single report, ideal for weekly cleans during the end-of-month invoicing rush.

It also suits administrators migrating users between Microsoft 365 and Google Workspace, where historic aliases sometimes receive residual spam. A batch check across the old aliases confirms whether new traffic is genuinely from partners or simply spoofed.

Integrating the API

For organisations wanting automation, the developer API lets you score any domain programmatically and embed the verdict inside your own systems. A Brisbane accounting firm, for example, can pipe the result into its practice management software so every new client onboarding message is tagged with a trust indicator before a staff member clicks.

The same approach suits cybersecurity teams operating under the Essential Eight maturity model, who need auditable evidence of email authentication across third-party suppliers. Because the API returns structured data, it feeds neatly into dashboards and SIEM platforms.

Safer handling of attachments

Attachments remain a leading infection vector, and Australian SMBs are often targeted through fake invoices, purchase orders and shipping notices. Before you save a file, you can check the trust status of the sender using this practical guide, which walks through the steps for screening attachments safely.

The guide recommends pairing a domain check with a sandboxed preview, keeping macros disabled in Office files, and confirming that any shared link matches the verified domain exactly. These habits are particularly valuable for tradies, consultants and remote teams receiving job briefs from new clients across different states.

Building a long-term routine

Domain validation works best when it becomes a habit. Setting aside five minutes at the start of each week to scan overnight messages, bulk-check recurring senders and review any low scores keeps your inbox defensible without slowing you down. Over time, you will recognise patterns criminals reuse, such as urgency around tax lodgement dates or fake delivery reschedule notices.

Pair this routine with the platform's ongoing monitoring, which alerts you when a trusted sender's configuration drops. That combination of proactive checking and continuous watching turns email into a manageable, transparent channel for Australian professionals.