12.4.2.4 VRFY Command Support

Keywords: domainvrfy, localvrfy, vrfyallow, vrfydefault, vrfyhide

The VRFY command enables SMTP clients to send a request to an SMTP server to verify that mail for a specific user name resides on the server. The VRFY command is defined in RFC 821.

The server sends a response indicating whether the user is local or not, whether mail will be forwarded, and so on. A response of 250 indicates that the user name is local; a response of 251 indicates that the user name is not local, but the server can forward the message. The server response includes the mailbox name.

Sending a VRFY Command

Under normal circumstances there is no reason to issue a VRFY command as part of an SMTP dialogue. The SMTP RCPT TO command should perform the same function that VRFY does and return an appropriate error. However, servers exist that can accept any address in a RCPT TO (and bounce it later), whereas these same servers perform more extensive checking as part of a VRFY command.

By default, the MTA does not send a VRFY command (the novrfy keyword is enabled).

If necessary, the MTA can be configured to issue the SMTP VRFY command by including the domainvrfy or localvrfy keyword in the channel definition. The keyword domainvrfy causes a VRFY command to be issued with a full address (user@host) as its argument. The localvrfy keyword causes the MTA to issue a VRFY command with just the local part of the address (user).

Responding to a VRFY Command

The vrfyallow, vrfydefault, and vrfyhide keywords control the SMTP server’s response when a sending SMTP client issues an SMTP VRFY command.

The vrfyallow keyword tells the MTA to issue a detailed, informative response. The vrfydefault tells the MTA to provide a detailed, informative response, unless the channel option HIDE_VERIFY=1 has been specified. The vrfyhide keyword tells the MTA to issue only a vague, ambiguous response. These keywords allow per-channel control of VRFY responses, as opposed to the HIDE_VERIFY option, which normally applies to all incoming TCP/IP channels handled through the same SMTP server.