Group Mailing lists on Leopard Server

Our school recently upgraded from Jaguar server, where this was so simple I didn't even have to think about it. Now in Leopard Server, I can't get this to work to save my life. I want to be able to address a message to a group, e.g. group@mydomain.com. I followed Apple's instructions to the letter (check the box in server admin, enable the group in workgroup manager, etc), and spent the better part of two days on the Internet searching for a solution. Relevant info: To the outside world, server is mail.mydomain.com. This also works internally. The server also has an name on the private in-house network of server.mydomain2.com. In SA, domain name is mydomain2.com, host name is mydomain.com (these seem to work, after trying many combinations of server names). In WGM, the group has services enabled at mail.mydomain.com, and the 'mailing list' box is checked. If I try to send a message to group@mydomain.com, I get 'user not set up for mail' errors. Messages to user@mydomain.com get thru, both inhouse and outhouse. I've seen posts that recommend stopping and starting the service, and I notice that in SA under Mail, Mailing lists shows as "starting up" for a long time, then shows "stopped". Maybe I'm getting close. Also, in Directory (leopard), clicking on the "mailing list" button addresses a message to group@server.mydomain2.com... not what I want. What do I have to do to enable a group as an email address that sends mail to all users in a group. This was so seamless in 10.2, but now I'm tearing my hair out over something I thought would/should be so simple. My users badly need to be able to send messages to groups of users. Thanks in advance for all help and insight. ---- Obbie