Limiting hosts for relay

[Ericx]

I want to limit the number of hosts that can relay email.

In Exchange I can say only relay from 192.168.0.10, 192.168.0.20, and only for mydomain.com.

Why? Lets say someone gets a virus or rogue application on their computer I don't want these computers sending email. Currently I can log onto any computer on the local subnet and send an email from myself to anyone without authenticating.

I've tried using 127.0.0.0/8 192.168.0.10/32 192.168.0.20/32
under the MTA and no luck.

[jholder]

If they are using TLS auth for outlook, etc, I think that trumps mynetworks.
Turn off TLS, and use mynetworks, and it should work.