Here's the problem... Sending a mail from one user to another user (internal), the name is spelled wrong (domain is correct). It takes a week for the sender to get a reply saying it is Undeliverable. However, when the same message is sent from an external (such as Yahoo), the Yahoo sender is notified immediately that it is Undeliverable! Why the difference and how can we fix it so the internal users are notified immediately as well.????? Thanks