Which port does SMTP use by default?
A.
TCP port 21
B.
TCP port 25
C.
UDP port 25
D.
UDP port 21
Explanation:
SMTP uses TCP port 25.
Incorrect Answers:
A: TCP port 21 is used for FTP.
C: SMTP uses TCP.
D: Port 21 is for FTP, but is TCP, not UDP.