Postfix relay problem

[Luc MAIGNAN]

Hi all,


my mail server provides an stmp access. I thought I've configured it to 
deny relay. It is true when I try basically to send a mail to another 
domain. But some persons seem to bypass this policy using themself a 
relay domain ::

24BDEE7918: to=<donna at go4extreme.com>, 
relay=smtp1.msp.securence.com[216.17.3.48]:25, delay=3.3, 
delays=0.02/0.01/1.2/2.1, dsn=2.0.0, status=sent (250 OK, queued as 
<20070429143657.24BDEE7918@

How can I deny these mails, and deny use of another relay ?

Many thanks
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