A Send Task is used to send a message. In Camunda this is done by calling Java code.

The Send Task has the same behavior as a Service Task.

<sendTask id="sendTask" camunda:class="org.camunda.bpm.MySendTaskDelegate" />

Camunda Extensions

Attributes
camunda:asyncBefore, camunda:asyncAfter, camunda:class, camunda:delegateExpression, camunda:exclusive, camunda:expression, camunda:jobPriority, camunda:resultVariable, camunda:topic, camunda:type, camunda:taskPriority
Extension Elements
——-
camunda:failedJobRetryTimeCycle, camunda:field, camunda:connector, camunda:inputOutput
Constraints
——-
One of the attributes `camunda:class`, `camunda:delegateExpression`, `camunda:type` or `camunda:expression` is mandatory
	The attribute `camunda:resultVariable` can only be used in combination with the `camunda:expression` attribute
	The `camunda:exclusive` attribute is only evaluated if the attribute `camunda:asyncBefore` or `camunda:asyncAfter` is set to `true`
	The attribute `camunda:topic` can only be used when the `camunda:type` attribute is set to `external`.
	The attribute `camunda:taskPriority` can only be used when the `camunda:type` attribute is set to `external`.

原文: https://docs.camunda.org/manual/7.9/reference/bpmn20/tasks/send-task/