kumomta/docs/reference/kumo/make_queue_config/egress_pool.md

egress_pool

The name of the egress pool which should be used as the source of this traffic.

If you do not specify an egress pool, a default pool named unspecified will be used. That pool contains a single source named unspecified that has no specific source settings: it will just make a connection using whichever IP the kernel chooses.

See kumo.make_egress_pool().