Milter-greylist

Mart Pirita wrote:
>> Great script but why to use DNSBL with milter-greylist instead of
>> using it with MTA? I'm using milter-greylist for greylisting and
>> sendmail as MTA with Spamcop DNSBL.

shuttlebox wrote:
> Because with the MTA you can only block mail with RBL:s. With 
> greylisting you can use RBL:s to block *or* to have a longer 
> greylisting period for example. Also much of the access rules of 
> Sendmail can be done in milter-greylist with much more ease.

I should further elaborate.  Spamcop already operates an RBL at
bl.spamcop.com.  However, it doesn't work with newly activated
zombies.  By taking a look at the top offending IP blocks, you can
discriminate against systems on networks known to be easily
compromised (like a lab whose machines are slowly getting infected).
This is a buffer-zone kind of RBL, which is not (to my knowledge)
served via DNS in the same manner as Spamhaus and Spamcop.

However, you would never want to block them outright, since they're
not known spammers (yet).  By delaying their mail, you give the
blacklists time to receive reports, and then Spamassassin can kill
them when it checks those blacklists.