denying email from your own domain but external IP's?

[Ugo Bellavance]

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Matt Kehler wrote:
> I'd like to toss all email if the 'from' address is of my own domain
> (xyz.com), and it does NOT originate from my internal 192.168.1.0/24
> network.  Can I do this with MailScanner?  Or can I even do it with
> Sendmail itself instead?  
> 
> Basically in our environment, people can use our internal mail client
> while at work, or they can use our webmail, but thats IT.  (ie, no
> Outlook express clients at home :).  So essentially anything with the
> 'from' as xyz.com and NOT using our internal IP addressing would have to
> be forged.

Forwarded by Ugo for Steve:

Check out this "clams to be us sendmail test which blocks email on bad
HELO/EHLO information:

http://www.cs.niu.edu/~rickert/cf/bad-ehlo.html

We just installed this test at a site that was getting hammered with
spam and viruses from email addresses pretending to be from their
domain. It stopped these attacks cold.

Steve

Steve Swaney
steve at fsl.com
www.fsl.com

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