[afnog] control forged emails using the sender_access on Postfix

[Peter Nyamukusa]

Hi folks,

I am trying to control forged originating email address by using the
sender_access file from my internal clients.
At first all I did was simply list the domains I wanted to reject as below

aol.com                 reject STOP SPAMMING We are watching you !!!!
hotmail.com             reject STOP SPAMMING We are watching you !!!!
bigfoot.com             reject STOP SPAMMING We are watching you !!!!
yahoo.com               reject STOP SPAMMING We are watching you !!!!
yahoo.co.uk             reject STOP SPAMMING We are watching you !!!!
gmail.com               reject STOP SPAMMING We are watching you !!!!
rock.com                reject STOP SPAMMING We are watching you !!!!

now it look like the spammer keeps changing his domain so I have decided to
instead block all domains and only just allow my domains. I have put this as
the first entry 
*   REJECT
Mydomain1.com OK
Mydomain2.com OK
......Etc

But it looks like the system is now completely open is there a way by
default to block all domains them allow only your domains, I have googled
around with no success, I trying to avoid having to manually add the
rejected domain every time it changes.

Thanks in advance

Cheers

Peter Nyamukusa
MCSE, Linux+ CCIP, JNCIS, A+