Which SMTP command is used to verify the actual delivery addresses of recipients?

• A. RCPT TO
• B. VRFY
• C. EXPN
• D. DNS zone transfer

Answer: (B)

Verifying actual delivery addresses is done by asking the SMTP server to confirm that a specific mailbox exists on that server. The VRFY command serves this purpose by requesting validation of a given user address; a positive response indicates the address exists and can receive mail, while a negative response means it does not. This differs from the command used during the actual delivery flow to specify recipients, which is a step in establishing whether the server will accept mail for those addresses. Another command mentioned, EXPN, is for expanding mailing lists into their members, not for validating individual addresses. DNS zone transfer is a DNS operation and not part of SMTP at all. In practice, many servers disable VRFY to prevent email address harvesting, but conceptually VRFY is the command designed to verify recipient addresses.