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Why am I still getting spam? – An insight into spam filters

So how does a SPAM filter work?

Throughout the world, billions of spam emails are sent every day, ranging from cryptocurrency scams and AI-generated phishing attempts to sophisticated deepfake voice messages asking you to update your details. We’re so much more aware of spam now that cybercriminals are using artificial intelligence and machine learning to create increasingly convincing attacks.

Some of the subject lines such as “urgent AI investment opportunity” and “your account requires immediate verification” we know you’ll recognise and delete, but the more sophisticated AI-generated ones are creating heightened risk for organisations across New Zealand.

Spam remains a massive problem. Our enterprise-grade filters process millions of emails monthly for our clients, with legitimate email typically representing only 15-20% of all incoming messages. The rise of AI-powered spam has made detection more challenging, but modern filtering systems have evolved to meet these threats.

Not all spam is created equal—there’s actually a sophisticated scoring system for email threats. For an email to be considered legitimate, it needs to pass multiple layers of security criteria. Each criterion is weighted depending on the threat level if the email doesn’t meet particular requirements.

Modern spam filters assess multiple areas:

• Sender reputation and authentication (SPF, DKIM, DMARC records)
• Content analysis using machine learning algorithms
• Behavioural patterns and anomaly detection
• Real-time threat intelligence feeds
• AI-powered image and attachment scanning

If an email passes all the criteria, it’s delivered straight to your inbox. But if it matches some problematic criteria, or triggers particularly concerning flags, it will either be quarantined for review or blocked entirely.

Why am I still getting spam in 2026?

Spam filters have become incredibly sophisticated, but cybercriminals are leveraging AI and machine learning to stay ahead. According to CERT NZ, new attack vectors and AI-generated content are making detection increasingly challenging.

You might also be inadvertently making yourself a target. Publishing email addresses on websites, using predictable email formats (like firstname.lastname@company.co.nz), or having poor email authentication can increase your spam exposure.

6 actions to reduce the amount of spam you receive

• Report emails as spam – Use your email client’s reporting features. This helps train AI filters and builds threat intelligence databases.
• Implement proper email authentication – Ensure your organisation uses SPF, DKIM, and DMARC records to prevent spoofing of your domain.
• Never engage with suspicious emails – Don’t click links, download attachments, or reply. Modern spammers use engagement tracking to validate active accounts.
• Use enterprise-grade email security – Consumer email services can’t match the protection offered by business-focused solutions with advanced threat protection.
• Educate your team regularly – Human awareness remains crucial as attacks become more sophisticated.
• Review email handling policies – Ensure staff understand when and how to share email addresses, and implement procedures for reporting suspicious emails.

The primary rule with spam remains unchanged: if in doubt, don’t engage with the email. For organisations in the legal, health, NGO, and government sectors, the stakes are particularly high given the sensitive data you handle.

Our team regularly updates our filtering systems with the latest threat intelligence and can provide detailed reporting on your organisation’s email security posture. If you’re concerned about your current email security or experiencing an increase in spam, we’d be happy to discuss how we can help strengthen your defences.

Chris Drowley
General Manager, Resolve Technology
Outside the office, Chris runs a highly organised empire of model trains — where the schedules are always on time, unlike the real thing.