The INBOUNDOPENLIMIT statement in the hlq.SMTP.CONFIG file has been coded.

limit_value is the maximum number of simultaneous TCP connections to be used by the SMTP server to receive inbound mail. The valid range is 2 - 256 or the value of 0. If 0 is coded then the SMTP server will not open up a listening connection at all and autolog cannot be used to monitor and restart the SMTP started procedure.

See the information about the INBOUNDOPENLIMIT statement in z/OS Communications Server: IP Configuration Reference.