How do I restrict my mail server from being an open relay?

OK, so if the Advanced Administration guide doesn't document how I can do this with 10.8.2/server 2.2 how can I do it?

So in the advanced admin guide at this page http://help.apple.com/advancedserveradmin/mac/10.8/#apdB3F8B86B-1839-4692-85FD-0 07FC7222B78

I can't do what it directs with the server app (replace server admin with server)?

1. In Server Admin, select a server in the Servers list, and then select Mail.
2. Click Settings, and then click Relay.

There is no Settings -> Relay?

1. Select “Accept SMTP relays only from these hosts and networks.”
2. Edit the list of hosts by choosing one of the following:
   • Click the Add button ➕ to add a host to the list.
   • Click the Remove button (–) to delete the selected host on the list.
   • Click the Edit button (/) to change a host on the list.
   When adding to the list, Server Admin accepts a variety of notations. You can:
   • Enter a single IP address or the network/netmask pattern, such as 192.168.40.0/21.
   • Enter a host name, such as mail.example.com.
   • Enter an Internet domain name, such as example.com.

MXToolbox was a really helpful confirmation step - thanks.