Securing Your Email Gateway: Best Practices Against BEC and Spoofing

Email remains central to business operations across Australia. Staff in Sydney, Melbourne, Brisbane and Perth use it to approve invoices, exchange customer information, coordinate suppliers and access cloud applications. That makes the email gateway a high-value control point for blocking fraud before it reaches an employee’s inbox.

Business email compromise (BEC) attacks often begin with a convincing message rather than obvious malware. Criminals may impersonate a chief executive, redirect a supplier payment or monitor a conversation before requesting a last-minute change to bank details. Spoofed domains and lookalike addresses make these requests appear legitimate.

Remote and hybrid work have widened the attack surface. Employees may review messages on mobile devices between meetings, from home networks or while travelling, reducing the time available to inspect headers and verify unusual requests. Strong technical controls must therefore be supported by practical processes that work under pressure.

Australian organisations also need to consider the Privacy Act 1988, the Notifiable Data Breaches scheme and the Spam Act 2003 when handling personal information and unsolicited messages. A reliable email security programme should reduce fraud risk while producing evidence for incident response, audits and regulatory reporting.

Understand How BEC And Spoofing Work

BEC commonly relies on account takeover, display-name impersonation, domain spoofing or a compromised supplier mailbox. Attackers may study public leadership profiles, previous invoices and staff signatures before entering an active email thread. The message can then appear familiar even though the payment instruction is fraudulent.

Email authentication helps distinguish legitimate senders from impostors. Sender Policy Framework (SPF) identifies permitted sending systems, DomainKeys Identified Mail (DKIM) applies a cryptographic signature, and Domain-based Message Authentication, Reporting and Conformance (DMARC) tells receiving servers how to handle failures. These controls should be configured for every corporate domain and reviewed when marketing, payroll or cloud platforms change.

Build A Strong Authentication Foundation

Start with an accurate inventory of domains, subdomains and third-party services that send email on the organisation’s behalf. Publish a restrictive SPF record, enable DKIM with protected keys and move DMARC from monitoring to quarantine or rejection after legitimate senders have been validated. DMARC aggregate and forensic reports can reveal spoofing attempts and misconfigured systems.

Multi-factor authentication should protect Microsoft 365, Google Workspace, webmail, administrator accounts and remote access. Phishing-resistant methods such as passkeys or hardware security keys provide stronger protection than passwords and SMS codes. Conditional access policies can also restrict risky sign-ins based on device health, location and unusual behaviour.

Inspect Messages Before They Reach Users

A secure email gateway should scan attachments, URLs, sender reputation and message behaviour. Sandboxing can detonate suspicious files, while time-of-click URL protection helps block links that become malicious after delivery. Impersonation detection should compare display names, reply-to addresses, sending domains and communication patterns.

Filtering should be carefully tuned rather than set and forgotten. Excessive blocking encourages staff to bypass controls, while weak filtering leaves dangerous messages in the inbox. Security teams should review quarantine trends, false positives and high-risk sender categories, including newly registered domains and external messages requesting payment or credentials.

Link Email Controls To Payment Processes

Technology cannot authenticate a changed bank account by itself. Australian businesses should require an independent verification step for new suppliers, altered payment details, urgent transfers and unusual payroll requests. Verification should use a trusted phone number or established contact, not details supplied in the suspicious email.

Finance and procurement teams need clear separation of duties. The person receiving a request should not be the only person approving and releasing funds. A short delay for confirmation is often far less costly than recovering money sent to a mule account, particularly when criminals exploit end-of-month processing or public holidays.

Monitor, Test And Respond Continuously

Centralised logging should capture authentication events, mail-flow decisions, administrator changes, suspicious forwarding rules and user-reported phishing. SIEM monitoring can correlate these signals with endpoint and identity data, helping analysts detect mailbox takeover, impossible travel and unusual forwarding to external addresses.

Independent testing can expose gaps that routine administration misses. A cybersecurity assessment team can review email configurations, simulate realistic phishing scenarios and assess how alerts and escalation procedures perform. Testing should include executives, finance staff, administrators and high-value shared mailboxes.

Practical Controls For Australian Organisations

A written standard makes secure behaviour repeatable across offices, remote workers and contractors. It should define who can approve payments, how incidents are reported, when accounts are suspended and which records must be retained. Staff need short, regular exercises that reflect real Australian business conditions, such as a supplier request arriving during a busy morning in Parramatta or a payroll change sent before a public holiday.

Use the following controls as a baseline:

• Enforce SPF, DKIM and DMARC across every business-owned domain.
• Require phishing-resistant multi-factor authentication for privileged and financial accounts.
• Block or quarantine risky attachments, macros, executable files and newly registered domains.
• Add independent verification for payment changes, credential requests and urgent transfers.
• Monitor mailbox rules, external forwarding, sign-in anomalies and privileged changes.
• Provide a clear reporting button and measure response times after simulated phishing exercises.

Review these measures at least annually and after mergers, new cloud deployments or major supplier changes. Organisations operating in regulated sectors should map email controls to internal risk registers, privacy obligations and relevant industry requirements.

Email protection works best as a layered programme: authenticated domains, secure identity, intelligent filtering, informed employees, verified payments and continuous monitoring. By combining these measures with structured vulnerability testing and incident response, Australian organisations can reduce the likelihood that a convincing message becomes a costly breach. Assess your email environment now, close the highest-risk gaps and establish monitoring that keeps pace with changing BEC tactics.