[Gllug] blacklisted mail servers

[Martyn Drake]

paul wrote on 20 October 2005 22:51:

> If a mail server is blacklisted by a company, but the people running
> the server are not guilty of spamming - I.E: they have been used as a
> spamming relay, does all mail get blocked or is it dependent upon who
> blacklists you?   

They will usually use something called a Realtime Blackhole List (see the
Wikipedia entry at http://en.wikipedia.org/wiki/DNSBL which will give a far
better explanation than I can about RBLs and DNSBLs).  It depends entirely
on the company as to which services they use.  Companies operating blacklist
services may choose to list an entire ISP/host if they feel that the
ISP/host are not making sufficient efforts to purge spammers from their
network.  I seem to remember that Spews is quite well known for doing that
sort of thing.

Examples of RBLs include Spamhaus (http://www.spamhaus.org), ORDB and
Blackholes.us (which you could use to block entire countries!).

In short, the people running the blacklisted server may just be unfortunate
to have an IP address which falls within a range contained within a
particular RBL organisation's database.  They need not have done anything to
get in it.  The only thing they can do is to find out which RBL they're in
and ask them why they're in it.

A handy tool to check your mail server against multiple RBLs is available at
http://www.dnsstuff.com.

Regards,

	Martyn


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