TCP/IP-channel-specific options: DISABLE_CIRCUIT (0 or 1)
The MTA's SMTP server implements a private command XCIR. This command returns MTA circuit check information. Releasing such information may consistute a breach of security for some sites. Setting the SMTP server option
DISABLE_CIRCUIT to 1 disables the XCIR command, so that the SMTP server responds with the error
550 5.7.0 XCIR command has been disabled.
to any XCIR command attempts. Setting
DISABLE_CIRCUIT to 0 enables the XCIR command. If
DISABLE_CIRCUIT is not explicitly set, then use of the XCIR command is controlled by the
DISABLE_GENERAL TCP/IP-channel-specific option setting. In 8.0, the default has changed to 1, disabling the XCIR command.
SMTP server probes of the PORT_ACCESS mapping table can enable use of XCIR (overriding a more general
DISABLE_GENERAL=0 setting) for connections from particular source IPs (e.g., the host itself, 127.0.0.1, and particular administrator systems) via the (new in Messaging Server 7.0)