PC Magazine – 6 Ways SMBs Can Avoid an Email Security Nightmare

ATP – Safe Attachments, Safe Links, and Anti-Phishing Policies or “All the policies you can shake a stick at”

Australian Cyber Security Centre (ACSC) – Malicious Email Mitigation Strategies

Avanan – 6 Things You Need to Know About Microsoft Security in Office 365

NIST SP 800-45 Guideline on Electronic Mail Security

Tech Target – Email Security Best Practices