Sendmail: How does one blacklist annoying spammers?

[Daniel B. Thurman]

On 06/25/2010 02:56 PM, Greg Woods wrote:
> On Fri, 2010-06-25 at 14:46 -0700, Daniel B. Thurman wrote:
>    
>> I thought it was sufficient to look into the headers
>> of the offending email spammmers and add these respective
>> IP address and/or host names to the /etc/mail/access file,
>>      
>
> Attempting to block the sender addresses will never work because they
> can so easily be forged. Attempting to block IP addresses of spammers by
> hand will not work either. Spammers these days use botnets, networks of
> thousands of compromised boxes, so that their IP addresses change
> rapidly. By the time you discover and enter one of their IP's, they've
> already moved on to another one.
>    
Yes, that makes sense...
> What you need is a DNS-based block list which is maintained by people
> who are dedicated to keeping it up to date. This isn't perfect either
> but the reaction is far faster than you can ever do yourself. I use the
> Spamhaus XBL/SBL (www.spamhaus.org) for this both at work and at home;
> it catches 10 times more spams than our SpamAssassin-based content
> filters do.
>
> --Greg
>    
Are you talking about something like this from sendmail.mc:

FEATURE(`dnsbl', `relays.ordb.org', `"Rejected due to Open Relay see 
http://www.ordb.org/lookup/?host=" $&{clientaddr} " for more 
information"')dnl