grep filters to block open relay

Kai Schaetzl maillists at
Fri Mar 24 00:31:19 GMT 2006

Hermit921 wrote on Thu, 23 Mar 2006 14:28:23 -0800:

> They can't or won't configure Exchange to accept mail only if the 
> recipient address is valid

AFAIK, Exchange *can* be configured to not be an open relay.

> at

The relay tests don't work this way. They will try to send email with some 
tricks to addresses that are not on your machine. This includes tricks 
like the above. But accepting and dropping such a mail will possibly not 
get you on such a list. Only if that mail is received in their spamtrap 
then you qualify as an open relay, just accepting and not forwarding it is 


Kai Schätzl, Berlin, Germany
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