220-802 · Question #8
While configuring a new email application that uses POP3 for a customer, the technician determines the firewall is blocking the traffic. Which of the following ports should be opened to allow POP3…
The correct answer is B. 110. POP3 (Post Office Protocol version 3) uses TCP port 110 for unencrypted mail retrieval, and this port must be open in the firewall for the email client to receive messages.
Question
While configuring a new email application that uses POP3 for a customer, the technician determines the firewall is blocking the traffic. Which of the following ports should be opened to allow POP3 mail traffic through the firewall?
Options
- A53
- B110
- C443
- D3389
How the community answered
(33 responses)- A3% (1)
- B88% (29)
- C3% (1)
- D6% (2)
Why each option
POP3 (Post Office Protocol version 3) uses TCP port 110 for unencrypted mail retrieval, and this port must be open in the firewall for the email client to receive messages.
Port 53 is used by DNS (Domain Name System) for name resolution queries and has no role in POP3 email retrieval.
POP3 is defined in RFC 1939 and operates over TCP port 110 for standard (unencrypted) connections. The firewall must permit inbound and outbound traffic on port 110 to allow the email application to authenticate and download messages from the mail server.
Port 443 is used for HTTPS (TLS-encrypted web traffic) and for secure email protocols such as SMTPS or POP3S, but not for standard unencrypted POP3.
Port 3389 is used by RDP (Remote Desktop Protocol) for remote desktop connections and is entirely unrelated to email protocols.
Concept tested: POP3 default port number (110)
Source: https://learn.microsoft.com/en-us/exchange/clients/pop3-and-imap4/pop3-and-imap4
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