Why can't external people email a distribution group email address on Windows SBS 2008 server
I have a windows 2008 SBS server and I can email various email addresses/mailboxes within the exchange server. I setup a distribution group firstname.lastname@example.org using the wizard withing the Exchange Managment Console. I can email email@example.com from within the organisation (i.e. mailboxes on the exchange server) however I cannot email from outside the exchange server. I get a returned message as follows ...
Your message did not reach some or all of the intended recipients.
Subject: Test 03
Sent: 08/09/2010 15:06
The following recipient(s) cannot be reached:
firstname.lastname@example.org on 08/09/2010 15:06
The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator.
< smtp.server.com #5.0.0 X-Postfix; host x.x.x.x[x.x.x.x] said: 550 5.1.1 User unknown (in reply to RCPT TO command)>
x.x.x.x is the IP address of my firewall who has a NAT and firewall rule to allow mail through to the exchange server. This is working as I do recieve emails for the other mailboxes.
Any ideas on where the restriction is? I thought it might be that the distribution group is set to only work internally but I cannot find the setting to change it.