If a message is returned to you, there are several possible reasons why. The address you used could be wrong. Check and make sure you typed in the address exactly as it should be. There could be a server down at the "other end." Verify you used the correct address and try to send it again. You can always check the address book at their web site if one is available. If you have tried to send to a particular address multiple times and have verified that the address is correct, but you still are receiving undeliverable messages, forward the "Undeliverable" message to the UWSP Postmaster and they will look into the situation for you.