Email Authentication: SPF, DKIM, and DMARC
SPF (Sender Policy Framework)
SPF specifies which mail servers can send email on behalf of your domain. Receiving servers check SPF records to verify sender legitimacy.
DKIM (DomainKeys Identified Mail)
DKIM adds a digital signature to outgoing emails. Recipients can verify the signature to confirm the email hasn't been tampered with.
DMARC (Domain-based Message Authentication)
DMARC builds on SPF and DKIM, telling recipients what to do when authentication fails. It also provides reporting on email authentication results.
Microsoft 365 Email Security Features
- Exchange Online Protection: Basic spam and malware filtering included in all plans
- Microsoft Defender for Office 365: Advanced threat protection with safe links and safe attachments
- Anti-phishing policies: Impersonation detection and protection
- Data loss prevention: Prevent sensitive information from being sent externally
User Training
Technology alone isn't enough. Train users to:
- Recognise phishing indicators (urgency, unusual requests, suspicious links)
- Verify requests through separate channels before acting
- Report suspicious emails to IT
- Never enter credentials from email links
How We Researched This Article
This article was compiled using information from authoritative industry sources to ensure accuracy and relevance for Australian businesses.
Sources & References
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Microsoft Email Authentication
Microsoft documentation on SPF, DKIM, and DMARC
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ACSC Email Security Guide
Australian Government email security guidance
* Information is current as of the publication date. Cybersecurity guidelines and best practices evolve regularly. We recommend verifying current recommendations with the original sources.
Frequently Asked Questions
Do I need all three: SPF, DKIM, and DMARC?
Yes. Each provides different protection, and DMARC requires both SPF and DKIM to function properly. Implementing all three is the standard for proper email authentication.
How do I check if my domain has email authentication?
Use online tools like MXToolbox or dmarcian to check your domain's SPF, DKIM, and DMARC records. Many businesses are surprised to find missing or misconfigured authentication.
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