SMTP VRFY Command for User Enumeration

312-50v13 By islever Editorial Last updated

Enumeration

Short answer

C The VRFY command verifies if a specific user exists on the SMTP server.

Question

Which of the following commands checks for valid users on an SMTP server?
  1. RCPT
  2. CHK
  3. VRFY Correct Answer
  4. EXPN

Key Takeaways

Tests knowledge of SMTP enumeration commands, specifically distinguishing between verifying a single user (VRFY) and expanding a mailing list (EXPN).

The VRFY command in SMTP is used to verify if a specific email user exists on the server. This page explains why VRFY is the correct answer over EXPN and other options.

Common mistake: Candidates often confuse VRFY with EXPN. While VRFY checks a specific user, EXPN expands a mailing list, which might be misinterpreted as checking 'users' generally.

Expert Analysis

Why the Answer Is Correct

The VRFY (Verify) command is explicitly designed to check if a specific mailbox or user exists on an SMTP server. When sent with a username, it returns a status indicating whether that user is valid. This makes it a primary tool for user enumeration during reconnaissance.

Why the Other Options Are Wrong

RCPT TO specifies the recipient for a message but does not inherently verify existence without sending the message. CHK is not a standard SMTP command. EXPN (Expand) is used to expand a mailing list, showing all members, rather than verifying a single user's validity directly like VRFY.

Community Comment Notes

Community consensus strongly favors C. As one commenter noted, "The VRFY (Verify) command... is used to check if a specific user exists." Another highlighted the distinction: "as it asked for users it is D" was a minority view, but most agreed VRFY is the direct verification tool.

Exam Strategy

Memorize the specific purpose of each SMTP command. Distinguish clearly between VRFY (verify user) and EXPN (expand list) as they are frequently tested together.

Frequently Asked Questions

What is the difference between VRFY and EXPN?

VRFY verifies if a single specific user exists. EXPN expands a mailing list to show all its members.

Why is RCPT not the answer?

RCPT TO defines the recipient for a transaction but doesn't explicitly return a validity check response code for existence like VRFY does.

More 312-50v13 FAQ →

Community Votes

C
75%
D
25%

75% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 4 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 4

  1. killwitch 👍 1 Answered C
    The VRFY (Verify) command in SMTP (Simple Mail Transfer Protocol) is used to check if a specific user exists on the mail server. When an attacker or administrator sends VRFY <username>, the server responds with a confirmation if the user exists
  2. marcel9999 👍 1 Answered D
    as it asked for users it is D c: VRFY: This command asks the server to verify if a specific user exists.
  3. mulekule 👍 1 Answered C
    The command that checks for valid users on an SMTP server is VRFY
  4. Stithapragna 👍 1 Answered C
    The VRFY (Verify) command in SMTP (Simple Mail Transfer Protocol)

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