CPSA Port Numbers with Services and Protocols Practice Test 2026 - Free CPSA Practice Questions and Study Guide

Standard port numbers identify specific services in TCP/IP networks. POP3 is the protocol used to retrieve email from a mail server, and its default port is 110. This is the well-known port assigned for POP3, so clients connect to a server on port 110 to issue POP3 commands and receive responses (without TLS by default; a secure variant uses a different port). The other ports correspond to different services: 119 is NNTP (Usenet), 123 is NTP (time synchronization), and 563 is NNTP over TLS (NNTPS). So 110 is the appropriate port for POP3.