What is the default TCP port number used by SMTP for email submission with STARTTLS?

Options

  • A. 25
  • B. 587
  • C. 110
  • D. More than one of the above
  • E. None of the above

Correct Answer (Detailed Explanation is Below)

B. 587

Detailed Explanation

Explanation: TCP port 587 is the standard port for email message submission, commonly using STARTTLS to upgrade the connection to TLS encryption. Port 25 is traditionally used for mail server-to-server transfer.