Which of the following port numbers the POP3 protocol uses?

(A) 100
(B) 110
(C) 120
(D) 130

110 is the correct answer.

Post Office Protocol version 3 (POP3) – Port 110. POP3 is a standard mail protocol used to receive emails from a remote server to a local email client. POP3 allows you to download email messages on your local computer and read them even when you are offline. Note, that when you use POP3 to connect to your email account, messages are downloaded locally and removed from the email server.