OT - has my email domain been hijacked?

[kevin.kempter at dataintellect.com]

On Thursday 15 September 2005 18:08, Sam Varshavchik wrote:
> James Wilkinson writes:
> > Guy Fraser wrote:
> >> ...snip...
> >> Mail servers do not generally accept a DATA command if the RCPT
> >> command produces an error, so the rest of the headers are not
> >> looked at. The proper response is to respond with a user
> >> undeliverable error.
> >
> > That assumes that the receiving server knows that the address is
> > unknown.
> >
> > Very often (as with westexe.demon.co.uk), the MX (server to which
> > e-mails get sent initially) is owned by a big ISP (in my case Demon
> > Internet), which doesn't know which addresses on westexe.demon.co.uk are
> > valid. So it has to accept all e-mails to westexe.demon.co.uk.
>
> Tough cookies.
>
> Poor network design/configuration is not a valid excuse for a
> denial-of-service attack.
>
> I have several thousand IP addresses blacklisted, for trying to flood me
> with bounces to forged spam.
>
> Any mail server bouncing forged crap to me, for any reason, gets
> blacklisted.  End of story.
>
> > In this case, the relevant standards (RFC 821 and 2821) say that since
> > the e-mail has been accepted but can't be delivered, a bounce message
> > *must* be sent. (These days, there's enough spam and viruses about that
> > this is no longer considered best practice.)
>
> Correct.
>
> > In general, it's not easy to program a MTA to be sufficiently sure that
> > an e-mail *is* faked that it can drop it.
>
> Actually it is.  I've designed my mail server so that it should never
> generate backscatter.  Even due to traditionally difficult to anticipate
> situations, such as a mailbox over quota.
>
> It's not rocket science.  It can be done.  It has been done.

How do I blacklist an I.P. ?