Your Company's Email Server Has Been Filling Up Employee's Email

Multiple Choice

Your company's email server has been filling up employee's email boxes with advertisements for things they did not request. You have been asked to research how to stop these types of messages from getting to your coworker's email client software.  
What will you recommend to your supervisor?

A) Enable the firewall.
B) Enable the spam filter.
C) Enable port forwarding.
D) Enable MAC filtering.