Bidirectional, master, slave Channel Options

Initiating delivery processing
Three options are used to specify whether a channel is served by a master program, a slave program , or both. The default, if none of these options is specified, is. These options determine whether the MTA bothers to initiate delivery activity when a message is queued to the channel - there is no point in doing this on a slave-only channel.

The use of these options reflects certain fundamental characteristics of the corresponding channel program or programs. The descriptions of the various channels the MTA supports  indicate when and where these options should be used.

Note that the Job Controller configuration  should, normally, include definitions for what actual image(s) a channel should execute for   or   mode operations, as appropriate for that channel. For instance, a channel which is  (and where both directions are truly used) should normally have both   and   Job Controller options defined, whereas a channel which operates solely in   mode needs only a   option, not a.

See also:
 * Channel options
 * Channels
 * Available channels
 * Job Controller default configuration
 * master_command Option
 * slave_command Option
 * Processing control and job submission channel options
 * Channel options