Which SMTP command displays the actual delivery addresses of aliases and mailing lists?

Which SMTP command displays the actual delivery addresses of aliases and mailing lists?

• A. EXPN
• B. RCPT TO
• C. SMTP Relay
• D. VRFY

Answer: (D)

In SMTP, the command used to verify an address and, in some cases, reveal who actually receives mail for that address is VRFY. When you issue VRFY for an alias or mailing list, the server may respond with the real delivery addresses behind that alias. This behavior lets you see the actual recipients that a mailing list or alias resolves to, which is why it’s the best fit for displaying those underlying addresses in environments where the server discloses this information. RCPT TO is for naming the next intended recipient of the current message during the session; it doesn’t enumerate the members of an alias or list. EXPN is explicitly for expanding a mailing list, but many servers disable it to prevent disclosure of list members. SMTP Relay isn’t a direct command for listing recipients.

In SMTP, the command used to verify an address and, in some cases, reveal who actually receives mail for that address is VRFY. When you issue VRFY for an alias or mailing list, the server may respond with the real delivery addresses behind that alias. This behavior lets you see the actual recipients that a mailing list or alias resolves to, which is why it’s the best fit for displaying those underlying addresses in environments where the server discloses this information.

RCPT TO is for naming the next intended recipient of the current message during the session; it doesn’t enumerate the members of an alias or list. EXPN is explicitly for expanding a mailing list, but many servers disable it to prevent disclosure of list members. SMTP Relay isn’t a direct command for listing recipients.