IMTA creates service jobs (channel master programs) to deliver messages. The job controller, which launches these jobs, associates them with queues. Queue types are defined in the job_controller.cnf file. The queue type with which each channel's master program is associated can be selected on a channel-by-channel basis, using the queue keyword. The queue keyword must be followed by the name of the queue type to which delivery jobs for the current channel should be queued. The name of the queue type should not contain more than 12 characters. If the queue keyword is omitted, then the queue used is the default queue, the first queue listed in the job controller configuration file.