OK - yes it's a term I invented. Yellow listing is a DNS list of hosts
that are mailservers for big ISPs and other sources of mixed ham and
spam. yahoo, gmail, hotmail, comcast, aol are examples of hosts that
would be yellow listed.
Why yellow list? The idea of a yellow list is to prevent certain hosts
from being either white listed or blacklisted. For example, I live in
the US as do most of my customers. So email comping from yahoo.fr is
almost 100% spam. Left to automatic processes it wouldn't take long
before yahoo.fr servers got blacklisted.
Conversely, AOL has been doing a reasonably good job of stopping
outgoing spam. So good in fact that automatic processes started listing
aol servers on the whitelist. Thus when a spammer made it through AOL
they also bypassed SA on my servers because they were white listed.
I am now creating yellow list which have been what I have detected as
mixed source hosts, some spam and some ham. I have now added logic where
I look up the host name and if the host name matches a big ISP then I
yellow list it immediately. Once it is yellow listed then I bypass all
white/black list tests that might otherwise accept or reject the message
without SA testing.
I think it would be useful to start using this idea more widely to
improve the quality of DNS listing. So roll the idea around and see if
we can build on it.
Here's some info on how to use my lists.
http://wiki.ctyme.com/index.php/Spam_DNS_Lists
Feel free to experiment.
