Dan, Absolutely correct. The ONLY way for ensuring success is end-to-end reciepts/acks. While this is obviously true for SMTP, it is also true for ALL messaging methods. Some methods are more reliable so this is not as intuitive but it is still true. Say for example, I send an HTTP request and then my connection is dropped. Since DFN and Acks are also governed by Retries then if I stay offline for a period greater than the Retries * RetryInterval for the DFN or Acks, I will never receive either. Lack of a failure is not success. We cannot guarantee either an Ack or DFN on synchronous transports. The only means for determining success is an end-to-end Receipt/Ack. Whatever we do in the middle is just to increase reliability. David Fischer Drummond Group.
