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selection_strategy

Since: Dev Builds Only

The functionality described in this section requires a dev build of KumoMTA. You can obtain a dev build by following the instructions in the Installation section.

Optional string. Controls how a source is chosen from the pool each time a message moves from its scheduled queue into a ready queue.

The possible values are:

  • "WeightedRoundRobin" - the default. Every selection uses Weighted Round Robin across the entries, independent of any prior selection for the same message.

  • "StickyWeightedRoundRobin" - the first selection for a message uses Weighted Round Robin and the chosen source name is recorded in the message metadata as sticky_egress_source. Later selections for that message reuse the recorded source for as long as it remains an entry in the pool with a non-zero weight.

If the recorded source is no longer in the pool, a fresh selection is made and recorded. This can happen when the pool definition changes or the message is rebound to a queue that uses a different pool.

The recorded source is cleared when a message is transferred to another node via kumo.xfer.