In article <Pine.NEB.4.61.0501100026140.823@irina.net.flo>,
	Florian Stoehr <netbsd@wolfnode.de> writes:
> I want to block all (ALL!) SMTP traffic from the whole "attbi.com" 
> IP address range for my private mail server.

Try adding something like this in "/etc/hosts.allow":

sendmail: ALL EXCEPT .attbi.com

They'll be able to get a SMTP connection but not to deliver e-mail.
But I would really recomment to use a better technology like e.g.
Greylisting.

	Kind regards

-- 
Matthias Scheler                                  http://scheler.de/~matthias/