Sending an email to a known non-existent user is a reconnaissance technique used to:
Analyze bounce-back (NDR) messages.
Discover the email server’s operating system, filtering behavior, internal mail routing, and directory structure.
Reveal technologies such as Exchange, Postfix, etc.
From CEH v13 Official Courseware:
Module 2: Footprinting and Reconnaissance
CEH v13 Study Guide states:
“Sending a message to an invalid address can reveal error messages or NDRs that leak internal system details, such as mail server versions, spam filtering technologies, and internal naming conventions.”
Incorrect Options:
A: Not applicable.
B/C: Not the purpose here.
E: Anti-virus testing requires a separate controlled method.
[Reference:CEH v13 Study Guide – Module 2: Email Footprinting TechniquesRFC 3463 – Enhanced Mail System Status Codes, ======, , ]
