Sendmail: How does one blacklist annoying spammers?

[Genes MailLists]

On 06/28/2010 12:05 AM, Ed Greshko wrote:
> On 06/28/2010 11:56 AM, Tim wrote:
>> Only a few thousand?  What do you think is a huge list?  And that's just
>> your list of mail servers for one service...  What about the other ISPs,
>> the thousands of them?
>>   
> Having a look at the SPF records....
> 
> gmail.com.              300     IN      TXT     "v=spf1
> redirect=_spf.google.com"
> 
> which becomes...
> 
> _spf.google.com.        300     IN      TXT     "v=spf1
> ip4:216.239.32.0/19 ip4:64.233.160.0/19 ip4:66.249.80.0/20
> ip4:72.14.192.0/18 ip4:209.85.128.0/17 ip4:66.102.0.0/20
> ip4:74.125.0.0/16 ip4:64.18.0.0/20 ip4:207.126.144.0/20
> ip4:173.194.0.0/16 ?all"
> 
> and therefore totals to a potential +212K "approved" sending hosts.
> 
> But, as far as the SPF processing is concerned....note the ?all at the end.
> 
> 

  SPF ... bah its silly. Here's another reason not to use it ... DKIM is
much better. Not perfect but much better.

  This is google trying to compact the SPF record - those netblocks are
not all used for mail. If they didn't do this they would have very very
very long SPF records .. lol.

  Go after the hosts which actually send their mail outbound ... last I
checked its in the 2,700 zone.

  And no that's not a lot to whitelist at all ...

 gene/