You are definitely being too optimistic :-( In order to implement the new format, you need an intelligible delivery error to begin with. If your software says "An error occurred delivering your mail to one or more of its recipients" and leaves it at that, your existing code probably doesn't have access to the data that would be needed to implement the new format. I also doubt that this will catch up quickly. Sendmail will use it, and then a few products here and there, maybe. Implementing the new format doesn't provide much of a benefit to the site running the software, it just helps remote list owners. I expect it would be one of the last items in the wish lists. Eric