Which port is traditionally used for SMTPS (SMTP over SSL)?

• A. 587 TCP
• B. 465 TCP
• C. 25 TCP
• D. 110 TCP

Answer: (B)

SMTPS uses TLS from the moment the connection opens, meaning the TLS handshake happens before any SMTP commands. That implicit TLS approach traditionally used a specific port reserved for secure SMTP at connection start, which is the port commonly associated with SMTPS. So the traditional choice for SMTPS is that port.

In contrast, the other ports relate to different patterns: one is the standard SMTP submission path that starts plaintext and upgrades to TLS with STARTTLS, another is plain SMTP, and the last is for a different protocol (POP3). So the traditional SMTPS port is the TLS-at-connect option, which is why 465 is the expected answer.