[expert] Open Relay ?

[dennis]

Hi,

I have set up a mandrake 7.2 server with low security at IP 10.0.0.100.

Another machine at 10.0.0.30 running a php program used 10.0.0.100's smtp to
sent a email to an external
address and the message got thru.

Soon I will change 10.0.0.100 to a external IP.

Will this machine be an open relay ?

I understand that postfix > 19991227 will be protected against open relay?

I have checked my version to  be 19991231-pl08.

Is my machine ok ?

Thanks

Dennis