Your company has recently been experiencing high volumes of unsolicited bulk emails that are affecting employee productivity and potentially exposing the network to security risks. As the network administrator, you have been asked to recommend a solution to mitigate this issue. Which of the following would be an effective measure to prevent these spam emails from reaching user inboxes?
Upgrade the current email client software
Decrease the SMTP threshold for the network firewall
Implement a spam gateway to filter emails
Migrate from POP2 to POP3 or IMAPS
Limit the maximum size of incoming emails