TCP/IP channel option files control various characteristics of TCP/IP channels. Channel option files must be stored in the MTA configuration directory and named x_option, where x is the name of the channel. For example, msg-svr-base/config/tcp_local_option. For more information refer to 12.4.1 Configuring SMTP Channel Options. For complete information on all channel option keywords and syntax, see the Sun Java System Messaging Server 6.3 Administration Reference.