Which service uses TCP port 110 for mail retrieval?

Which service uses TCP port 110 for mail retrieval?

• A. Hypertext Transfer Protocol (HTTP)
• B. Simple Mail Transfer Protocol (SMTP)
• C. Post Office Protocol 3 (POP3)
• D. Network News Transfer Protocol (NNTP)

Answer: (C)

Port 110 is the standard TCP port for the Post Office Protocol version 3. POP3 is used by mail clients to connect to a mail server, retrieve messages, and optionally delete them from the server after download. It’s specifically designed for mail retrieval, which is why it’s the best fit for this question. The other options serve different purposes or use different ports: HTTP handles web traffic (port 80, or 443 for HTTPS), SMTP is for sending mail (ports like 25, 587, or 465), and NNTP is for Usenet news (port 119). So, for mail retrieval on port 110, POP3 is the correct association (note that a secure variant exists on port 995).

Port 110 is the standard TCP port for the Post Office Protocol version 3. POP3 is used by mail clients to connect to a mail server, retrieve messages, and optionally delete them from the server after download. It’s specifically designed for mail retrieval, which is why it’s the best fit for this question. The other options serve different purposes or use different ports: HTTP handles web traffic (port 80, or 443 for HTTPS), SMTP is for sending mail (ports like 25, 587, or 465), and NNTP is for Usenet news (port 119). So, for mail retrieval on port 110, POP3 is the correct association (note that a secure variant exists on port 995).