Bidirectional, master, slave Channel Options

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Initiating delivery processing (bidirectional, master, slave)

Three options are used to specify whether a channel is served by a master program (master), a slave program (slave), or both (bidirectional). The default, if none of these options is specified, is bidirectional. 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 master or slave mode operations, as appropriate for that channel. For instance, a channel which is bidirectional (and where both directions are truly used) should normally have both master_command and slave_command Job Controller options defined, whereas a channel which operates solely in master mode needs only a master_command option, not a slave_command.