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Your ISP offers email over POP3. What port number should be opened on your firewall to allow POP3 to work properly?

A) tcp/20

B) tcp/25

C) tcp/110

D) tcp/23

E) If I leave the port closed, I’ll finally have a clean inbox!

The answer: C) tcp/110

TCP port 110 is used for the Post Office Protocol version 3. This protocol is one of the most common used for email clients. Email servers generally communicate between each other using the Simple Mail Transfer Protocol (SMTP) over TCP port 25.

Want to know more? Watch “Common Ports.”

The fundamental languages used over our computer networks are a standard set of protocols that are used around the world. In this video, you’ll learn about protocols and the set of standards associated with TCP/IP. You’ll also learn the essentials of TCP/IP and how subnetting can be used to build today’s modern networks.