Re: [cobalt-users] Raq550: How do we Block spam with reverse DNS checks

[John D Gorena <Support@xxxxxxxxxxxxxxxxxxx>]

Dan Kriwitsky wrote:
> 
> > In the beginning of September 2003 a national realty company
> > (kw.com) started checking incomming email for reverse DNS
> > settings to help stop spam.  They report that most of the
> > spam has been blocked.  Only a few companies that did not
> > have any reverse DNS settings had problems but those
> > companies have fixed them thier dns settings.  Is there a way
> > that Raq550 owners can block Email from servers with no
> > reverse DNS settings?
> 
> This blocking was discussed in news.admin.net-abuse.email and many
> reported having to abandon it as too much legit mail was being blocked
> and it was an administrative headache.
> You might want to tail your maillog for a while and see what email is
> coming in with no rDNS and do a whois on the IPs. I could probably get
> away with it on my server, but I would hesitate to block customer email
> that way.
> 
> --
> C2003 Dan Kriwitsky


My clients complain about the spam.  About 80% of all their email is spam and
they are sick of it.  I appreciate your caution but I would like that procedure
to stop those servers that do not have a rDNS setting.  They are dedicated
Raq550's and they want a better filter.  In fact many of them deal with kw.com
and they got good reports back.  kw.com just checks to see if there is a rDNS. 
It does not have to match the sender domain.

John