try_next_host_on_transport_error

Since: Version 2025.10.06-5ec871ab

The functionality described in this section requires version 2025.10.06-5ec871ab of KumoMTA, or a more recent version.

An optional boolean value that defaults to false.

When set to true, if an SMTP message delivery attempt encounters a timeout, a transport error, or a protocol error that isn't directly associated with the message (eg: rejection prior to MAIL FROM), then, after logging a TransientFailure for the failed attempt, the message will be immediately eligible for delivery on the next available connection in the current connection session.

If there are no further available connections, or try_next_host_on_transport_error is set to false, then the message will be re-queued to the scheduld queue for later delivery.

In earlier versions of KumoMTA this option did not exist and the system behaves as if it was set to false.