If you want a step in your process model to go to another step when an error occurs, use error transition.

For example, use error transition type to go from the SendReceiptAck step to Wait for External Document step, when acknowledgement delivery fails.

If you want SendReceiptAck step to transition to an error step after 10 retries, add a transition to ExceptionHandler step with Transition Type as Step Iterations Exceeded.

For more information on error transitions, see Administering webMethods Process Engine.