Clients on a particular network are reporting that they have not been receiving e-mails since a new router was installed. You determine that it is a firewall issue. Which port is likely being blocked on the firewall?
80
443
110
23
Answer: 110
Notes:Port 110 is assigned by default to Post Office Protocol 3 (POP3). POP3 is used to retrieve e-mail from a server. It is often used in conjunction with Simple Mail Transfer Protocol (SMTP) which delivers the e-mails to the e-mail server.