The Federal Bureau of Investigation (FBI) has released an article on Building a Digital Defense with an Email Fortress. FBI warns that scammers commonly target business email accounts with phishing and social engineering schemes. Strategies for preventing email compromises include avoiding the use of free web-based email accounts; using multi-factor authentication; and updating firewalls, antivirus programs, and spam filters.
US-CERT encourages users and administrators to review the FBI article for more information and refer to US-CERT Tips on Using Caution with Email Attachments and Avoiding Social Engineering and Phishing Attacks.