I have created some distribution list. When I try to send an email to one of
these list, the List name appears in the to: address section, it is in bold
and has the + sign next to it. If you click on the + sign it shows all of
the addresses in the list. When I send the email I get an undeliverable
email back that states: (I set up a test group to try and resolve the problem)

Your message did not reach some or all of the intended recipients.

Subject: Just a test
Sent: 3/7/2010 10:49 AM

The following recipient(s) cannot be reached:

'Test Group' on 3/7/2010 10:49 AM
Invalid recipient

Does anyone have any idea how to correct this problem. All help is
appreciated.