rejecting botnets with sendmail

[Ugo Bellavance]

Andoni Auzmendi wrote:
> Experiencing the recent increase in spam from botnets, is there a way to
> reject (or discard) connections coming from servers containing their ip
> address within the hostname? I can see lots of connections from
> broadband or dialup addresses. Some of them even bypass greylilst as
> they resend the messages several times. We use Sendmail here and I guess
> there must be a milter which is capable of doing that.

Using the latest version of milter-greylist (3.0 RC6), you can impose 
greylisting based on DNSbl.  If you're not ready to block at sendmail 
based on DNSbl, this might be a softer approach.

Ugo