On Thu, 2008-10-30 at 10:28 -0600, Karl Pearson wrote:
> On Wed, 29 Oct 2008, Chris Arnold wrote:
> > We use zimbra OSS on SLES10 SP1. Zimbra has spamassassin built-in. At the
> > present time, my mailbox is filled with backscatter; getting around 10 a
> > minute since 4:30 today. I have postfix backscatter rules in postfix of
> > zimbra, http://www.postfix.org/BACKSCATTER_README.html#real but still getting
> > pounded. Here is the header from on such mail:
> >

Have you set up SPF records for your domain?

SPF records let the sites bouncing the spam discover that the sender has
been forged by the spammer. SPF can't eliminate all backscatter, but
should at least reduce the size of the barrage.

http://www.openspf.org/ describes SPF and has a tool for creating an SPF

http://www.kitterman.com/spf/validate.html provides additional tools for
testing SPF records.