getting Undeliverable messages back

I get a lot of "Undeliverable" messages back (directly to me, the submitter) after sending out a mail to our SmartList mailing lists. Example below. Can anybody tell me if I've got a problem with my Smartlist configuration, or if I need to do something to handle these? Presently, I've just redirected all of them to the list, hoping that it gets handled properly.

Thanks.

Lee Howard

--------------- Your message

To: mailing@1cachemail.com Subject: 1CACHE MOTHERSDAY NEWSLETTER Sent: Mon, 7 May 2001 12:17:46 -0600

did not reach the following recipient(s):

Rittenhouse Tim L Capt USAFA/DFC on Wed, 9 May 2001 09:25:55 -0600 Unable to deliver the message due to a recipient problem MSEXCH:MSExchangeIS:USAFA:FSXQPZ02 ---------------