Which of the following is the default port used by Simple Mail Transfer Protocol (SMTP)?

The correct answer is B. 25. SMTP uses TCP port 25 by default for mail transfer between servers, making it one of the oldest and most recognized well-known port assignments.

Network Traffic Analysis & Protocol Review

Question

Options

How the community answered

(30 responses)

A
7% (2)
B
73% (22)
C
7% (2)
D
13% (4)

Why each option

SMTP uses TCP port 25 by default for mail transfer between servers, making it one of the oldest and most recognized well-known port assignments.

A80

Port 80 is assigned to HTTP for web traffic and has no role in email transmission.

B25Correct

Port 25 is the IANA-assigned well-known port for SMTP, used for server-to-server email relay since RFC 821. It is the standard port mail transfer agents (MTAs) listen on to receive inbound messages from other mail servers.

C20

Port 20 is the FTP data transfer port used for active-mode file transfers.

D21

Port 21 is the FTP control port used to establish FTP sessions and send commands.

Concept tested: SMTP default well-known port assignment

Source: https://datatracker.ietf.org/doc/html/rfc5321

Topics

#SMTP#port numbers#email protocols#well-known ports

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