Final answer:
SMTP works on default ports 25 (standard SMTP), 465 (SMTP Secure), and 587 (Submission). These ports facilitate sending emails between servers. Port 465 is deprecated but still used by some systems.
Step-by-step explanation:
The Simple Mail Transfer Protocol (SMTP) is a protocol for sending email messages between servers. Most email systems use SMTP to send messages from one server to another; these messages can then be retrieved with an email client using either POP or IMAP. In terms of the default ports SMTP uses, they are:
- 25: This is the default SMTP non-encrypted port. It is widely used for sending emails but not encrypted, hence it is vulnerable to interception.
- 465: Historically used for SMTP Secure (SMTPS), which encrypts email transmissions. However, it has been deprecated but still in use by some services.
- 587: This port is used for submitting emails to a mail server for further delivery and uses encryption in the form of StartTLS or explicit SSL/TLS.
A correct answer to the student's question is the first set of port numbers: 1) 25, 465, 587. The other sets of numbers represent different protocols or services:
- 80, 443, 8080: These are standard ports for accessing the world wide web (HTTP and HTTPS).
- 110, 143, 993: These are related to retrieving email, with 110 being the port for POP3, 143 for IMAP, and 993 for IMAP over SSL/TLS.
- 20, 21, 22: These are related to file transfers and shell access, with 20 and 21 being FTP ports, and 22 being the port for SSH.