Which service uses port 25 by default?

Which service uses port 25 by default?

• A. Hypertext Transfer Protocol (HTTP)
• B. Kerberos—authentication system
• C. Simple Mail Transfer Protocol (SMTP)
• D. Trivial File Transfer Protocol (TFTP)

Answer: (C)

Port 25 is the standard port assigned for mail transfer between mail servers, which is what the Simple Mail Transfer Protocol uses. This protocol handles routing and delivery of email across the Internet. Other common services use different ports: HTTP typically uses port 80 (and 443 for HTTPS), Kerberos operates on port 88 (with some additional ports for related functions), and TFTP uses UDP port 69. So, the service that uses port 25 by default is the Simple Mail Transfer Protocol.

Port 25 is the standard port assigned for mail transfer between mail servers, which is what the Simple Mail Transfer Protocol uses. This protocol handles routing and delivery of email across the Internet. Other common services use different ports: HTTP typically uses port 80 (and 443 for HTTPS), Kerberos operates on port 88 (with some additional ports for related functions), and TFTP uses UDP port 69. So, the service that uses port 25 by default is the Simple Mail Transfer Protocol.