Errors on delivery of messages

I am a new Smartlist user, so please forgive any really obvious ignorance. The messages on my list are mostly getting delivered to the list members, but all of the messages delivered to my mailbox have the subject line "Mail delivery failed: returning message to sender" or something similar. The very bottom of this message will usually have the body of the message posted to the list by another user. Does anyone have any suggestions for making this delivery system resemble something a little more normal-looking? Tim Dees tim@timdees.com