I'm considering a DNS list that would return strings as TXT records that
contain key words that classify the Forward Confirmed rDNS name based on
a number of flags. For example, if the host is yahoo.com it might
contain "yellow freemail" indicating that it is yellow listed (mixed
ham/spam) and that it is a freemail provider. Here's some tags I'm
considering.

black - blacklisted
white - whitelisted
yellow - mixed source
nobl - nevr blacklist, but maybe whitelist
freemail - fre mail service like yahoo, hotmail, gmail
isp - isp consumer email servers - verizon, comcast etc. (mixed source)
dynamic - end user dynamic IP range

The idea being that there might be a number of different items that
returns useful information to help process email. Exim is capable of
processing these kind of conditionals. I'm not sure other MTAs are. SA
could be modified to process it.

Who likes this idea?