Which protocol uses port 25 by default for email transfer?

Which protocol uses port 25 by default for email transfer?

• A. HTTP
• B. SMTP
• C. POP3
• D. FTP

Answer: (B)

Email delivery relies on the Simple Mail Transfer Protocol. SMTP is responsible for moving messages between mail servers and from clients to servers, and by default it uses port 25 for this transfer. There are secure alternatives for submission or TLS-wrapped transmission (such as port 587 with STARTTLS or port 465 in TLS), but the default port associated with SMTP is 25, making it the correct choice. The other protocols serve different purposes: HTTP uses port 80 for web traffic; POP3 uses port 110 (with 995 for SSL) to retrieve mail from a server; FTP uses port 21 (with 20 for data transfer).

Email delivery relies on the Simple Mail Transfer Protocol. SMTP is responsible for moving messages between mail servers and from clients to servers, and by default it uses port 25 for this transfer. There are secure alternatives for submission or TLS-wrapped transmission (such as port 587 with STARTTLS or port 465 in TLS), but the default port associated with SMTP is 25, making it the correct choice. The other protocols serve different purposes: HTTP uses port 80 for web traffic; POP3 uses port 110 (with 995 for SSL) to retrieve mail from a server; FTP uses port 21 (with 20 for data transfer).