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TCP/IP-channel-specific options: HIDE_VERIFY (0 or 1)

The SMTP VRFY command can be used to establish the legality of an address prior to actually using it. Unfortunately this command has been abused by automated query engines in some cases. The SMTP server option HIDE_VERIFY, when set to 1, tells the MTA not to return any useful information in the VRFY command result; in particular, when HIDE_VERIFY=1 is set the MTA will, for arguments that are at least syntactically legal, return for addresses that syntactically might be "local" only:

252 2.5.0 Possible local address <address> 

or return the same response it returns regardless of HIDE_VERIFY setting for apparently remote addresses, namely:

252 2.5.0 Possible remote address not checked 

The default value is 0, which causes VRFY to act normally. See also the channel options controlling this behavior, vrfyallow, vrfydefault, and vrfyhide.

See also: