A system administrator has been tasked with allowing SMTP traffic through the system’s host-based firewall.

SMTP (Simple Mail Transfer Protocol) uses port 25 to send email messages between servers12.

SMTP uses port 25 to send email messages between mail servers. Therefore, the system administrator should enable port 25 to allow SMTP traffic through the host-based firewall. References: CompTIA A+ Certification Study Guide, Tenth Edition, pg. 282