User awareness education is the most effective method for reducing phishing attacks. Training users to recognize suspicious emails, links, and attachments can prevent them from falling for phishing attempts.
Technical solutions like SMTP filtering (C) and restricting emails (D) can help but are not as effective without user vigilance. A BYOD policy (B) does not directly address phishing email threats.
Reference: Core 2, Domain 2.4 - Security measures and social engineering.