Which of the following default port numbers need to be open on a firewall for a mail server to successfully send and receive mail? (Choose three.)
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A. B. C. D. E. F. G.BEF.
The correct answers for this question are B. 25, E. 110, and F. 143.
Explanation:
Email services use several protocols to send and receive emails. The most commonly used protocols for sending and receiving emails are Simple Mail Transfer Protocol (SMTP), Post Office Protocol version 3 (POP3), and Internet Message Access Protocol (IMAP).
SMTP is used for sending email messages, while POP3 and IMAP are used for receiving email messages.
The default port for SMTP is 25. So, if a mail server needs to send email messages, port 25 needs to be open on the firewall to allow outbound traffic.
The default port for POP3 is 110, and the default port for IMAP is 143. So, if a mail server needs to receive email messages using POP3 or IMAP, ports 110 and 143 need to be open on the firewall to allow inbound traffic.
Therefore, the correct answers are B. 25, E. 110, and F. 143.
The other port numbers mentioned in the question are not related to email services. Port 22 is used for SSH (Secure Shell), port 53 is used for DNS (Domain Name System), port 80 is used for HTTP (Hypertext Transfer Protocol), and port 161 is used for SNMP (Simple Network Management Protocol).