When the Internet Mail Service communicates with an SMTP host, it may be asked to identify a user. This is done with the SMTP verify command (VRFY). The verify command asks the receiver to identify whether a user can be reached through the receiving host. The response will include the mailbox of the user and a full name.
The following is an example of a verify request for the user "smith." The response is the full name and the SMTP address for the user Renee Smith.
Send: VRFY smith
Received: 250 Renee Smith <renees@abcd.COM>
The verify request for the Internet Mail Service is disabled by default. Disabling the VRFY command is of interest to mail administrators concerned with spoofing. The VRFY command is one method of querying a server for valid SMTP addresses.